MMC


Line plots across dimensions of each concept
Tables

Table of contents



us-gaap:CommonStockSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax
dei:LegalEntity
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments, us-gaap:Subsegments
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments, us-gaap:Subsegments
us-gaap:StatementGeographical, us-gaap:StatementBusinessSegments

us-gaap:OperatingExpenses

us-gaap:OperatingIncomeLoss
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:RetirementPlanType

us-gaap:InterestExpense

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

us-gaap:IncomeLossFromContinuingOperations

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxesPaidNet

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:Assets
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:AssetsCurrent

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:ReceivablesNetCurrent

us-gaap:OtherAssetsCurrent

us-gaap:PropertyPlantAndEquipmentGross
us-gaap:PropertyPlantAndEquipmentByType

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:PropertyPlantAndEquipmentNet
us-gaap:StatementGeographical

us-gaap:Goodwill
us-gaap:BusinessAcquisition
us-gaap:StatementBusinessSegments

us-gaap:IntangibleAssetsNetExcludingGoodwill

us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:OtherAssetsNoncurrent

us-gaap:LiabilitiesCurrent

us-gaap:DebtCurrent

us-gaap:LongTermDebtCurrent

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent

us-gaap:AccruedIncomeTaxesCurrent

us-gaap:DividendsPayableCurrent

us-gaap:LongTermDebt
us-gaap:DebtInstrument

us-gaap:LongTermDebtNoncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
dei:LegalEntity
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:MinorityInterest

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:TreasuryStockValue

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:RepaymentsOfLongTermDebt

us-gaap:PaymentsForRepurchaseOfCommonStock

us-gaap:RepaymentsOfLongTermDebt

us-gaap:EffectiveIncomeTaxRateContinuingOperations

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:ShareBasedCompensation

us-gaap:UnrecognizedTaxBenefits

us-gaap:DeferredTaxAssetsValuationAllowance
us-gaap:ValuationAllowanceByDeferredTaxAsset

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

mmc:AcquisitionRelatedHedgingExpense

mmc:AverageSharePriceCommonStock

mmc:BusinessCombinationConsiderationTransferredAssetsAcquired

mmc:BusinessCombinationConsiderationTransferredNoncontrollingInterestsAssumed

mmc:BusinessCombinationContingentandDeferredConsideration
us-gaap:BusinessAcquisition

mmc:CommonStockDividendsPerShareCashDeclared
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
mmc:DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations
us-gaap:RetirementPlanType

mmc:EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities
us-gaap:FairValueByLiabilityClass
mmc:FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments

mmc:IncreaseDecreaseinOperatingLeaseLiabilities
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
mmc:InterestIncomeFiduciaryAssets
us-gaap:StatementBusinessSegments

mmc:LeasesRightOfUseAssetAmortization

mmc:OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementBeforeTax

mmc:OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementNetofTax

mmc:OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementTax

mmc:OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentBeforeTax

mmc:OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentNetofTax

mmc:OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentTax

mmc:PaymentsForPreviousAcquisitionContingentConsideration
us-gaap:BusinessAcquisition

mmc:PaymentsForPreviousAcquisitionDeferredConsideration
us-gaap:BusinessAcquisition

mmc:PaymentsforAcquisitionsDeferredandContingentConsideration
us-gaap:BusinessAcquisition, us-gaap:LongtermDebtType
mmc:PaymentsforDerivativeSettlement

mmc:PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense
us-gaap:StatementEquityComponents
mmc:StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency
us-gaap:StatementEquityComponents
us-gaap:AdjustmentsToAdditionalPaidInCapitalOther
us-gaap:StatementEquityComponents
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

us-gaap:AllocatedShareBasedCompensationExpense

us-gaap:AmortizationOfIntangibleAssets

us-gaap:BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic

us-gaap:BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss

us-gaap:BusinessAcquisitionsProFormaRevenue
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationAcquisitionRelatedCosts

us-gaap:BusinessCombinationConsiderationTransferred1
us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationConsiderationTransferredLiabilitiesIncurred

us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:ChangeInUnrealizedGainLossOnForeignCurrencyFairValueHedgingInstruments1

us-gaap:CommonStockDividendsPerShareCashPaid

us-gaap:ContractWithCustomerLiabilityRevenueRecognized

us-gaap:ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents
us-gaap:CumulativeEffectOnRetainedEarningsNetOfTax1

us-gaap:DeferredIncomeTaxExpenseBenefit
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost
us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanOtherCosts
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanServiceCost
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedContributionPlanCostRecognized

us-gaap:Depreciation
us-gaap:StatementEquityComponents
us-gaap:DividendsCommonStockCash
us-gaap:StatementEquityComponents
us-gaap:DividendsShareBasedCompensationCash

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent

us-gaap:EquitySecuritiesFvNiRealizedGainLoss

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
us-gaap:FairValueByLiabilityClass
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByLiabilityClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease
us-gaap:FairValueByLiabilityClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases
us-gaap:FairValueByLiabilityClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements

us-gaap:FinitelivedIntangibleAssetsAcquired1
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:GainLossOnInvestments

us-gaap:GainLossOnSaleOfOtherAssets

us-gaap:GainsLossesOnExtinguishmentOfDebt

us-gaap:GoodwillAcquiredDuringPeriod

us-gaap:GoodwillOtherIncreaseDecrease

us-gaap:IncomeLossFromEquityMethodInvestments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:InvestmentType

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities

us-gaap:IncreaseDecreaseInAccruedIncomeTaxesPayable

us-gaap:IncreaseDecreaseInEmployeeRelatedLiabilities

us-gaap:IncreaseDecreaseInOtherCurrentAssets

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities

us-gaap:IncreaseDecreaseInReceivables

us-gaap:InterestPaidNet

us-gaap:InvestmentIncomeInterest

us-gaap:LaborAndRelatedExpense

us-gaap:LeaseCost
us-gaap:StatementEquityComponents
us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders
us-gaap:StatementEquityComponents
us-gaap:NoncontrollingInterestIncreaseFromBusinessCombination
us-gaap:StatementBusinessSegments
us-gaap:NumberOfBusinessesAcquired

us-gaap:OperatingLeaseCost

us-gaap:OperatingLeasePayments

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax

us-gaap:OtherComprehensiveIncomeLossTax

us-gaap:OtherCostAndExpenseOperating

us-gaap:PaymentsForDerivativeInstrumentFinancingActivities

us-gaap:PaymentsForProceedsFromInvestments

us-gaap:PaymentsForProceedsFromOtherInvestingActivities

us-gaap:PaymentsForRestructuring
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringCostAndReserve

us-gaap:PaymentsOfDividendsCommonStock

us-gaap:PaymentsOfFinancingCosts

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation

us-gaap:PaymentsToAcquireAdditionalInterestInSubsidiaries

us-gaap:PaymentsToAcquireBusinessesGross
us-gaap:BusinessAcquisition

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired

us-gaap:PaymentsToAcquireEquityMethodInvestments

us-gaap:PaymentsToMinorityShareholders

us-gaap:ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates

us-gaap:ProceedsFromIssuanceOfDebt

us-gaap:ProceedsFromIssuanceOrSaleOfEquity

us-gaap:ProceedsFromLinesOfCredit

us-gaap:ProceedsFromRepaymentsOfCommercialPaper

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
us-gaap:StatementEquityComponents
us-gaap:LongtermDebtType
us-gaap:RepaymentsOfDebt

us-gaap:RestructuringCharges
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve
us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve
us-gaap:ConsolidationItems, us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringCostAndReserve, us-gaap:Subsegments
us-gaap:BusinessAcquisition
us-gaap:RestructuringReserveSettledWithoutCash2
us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve

us-gaap:RestructuringReserveTranslationAdjustment
us-gaap:RestructuringCostAndReserve

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod

us-gaap:ShortTermLeaseCost

us-gaap:StockIssued1

us-gaap:SubleaseIncome
us-gaap:StatementClassOfStock
us-gaap:TreasuryStockSharesAcquired
us-gaap:StatementEquityComponents
us-gaap:TreasuryStockValueAcquiredCostMethod

us-gaap:VariableLeaseCost

us-gaap:WeightedAverageNumberDilutedSharesOutstandingAdjustment

mmc:AccruedFeesandOtherRevenueReceivableGrossCurrent

mmc:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansAdjustmentTax

mmc:AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax

mmc:AdvancedPremiumsandClaimsReceivableGrossCurrent
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
mmc:BusinessCombinationContingentConsiderationAssetFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
mmc:BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency
us-gaap:BusinessAcquisition
mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetsIncludingGoodwill
us-gaap:BusinessAcquisition
mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCashandInvestmentsHeldinFiduciaryCapacityNoncurrent
us-gaap:BusinessAcquisition
mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedFiduciaryLiabilitiesGrossNoncurrent
dei:LegalEntity
mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityDefinedBenefitPlanNoncurrent
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityForErrorsAndOmissions
us-gaap:BusinessAcquisition
mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent
us-gaap:BusinessAcquisition
mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseRightofUseAsset

mmc:CashCashEquivalentsRestrictedCashandRestrictedCashEquivalentsandFundsHeldinAcquisitionRelatedEscrow

mmc:CashandInvestmentsHeldinFiduciaryCapacityNoncurrent

mmc:DeferredTaxAssetsDeferredIncomeNetOfValuationAllowance

mmc:DeferredTaxAssetsNetNetOfValuationAllowance

mmc:DeferredTaxAssetsOperatingLossCarryforwardsDomesticNetOfValuationAllowance

mmc:DeferredTaxAssetsOperatingLossCarryforwardsForeignNetofValuationAllowance

mmc:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensionsAndPostretirementBenefitsNetofValuationAllowance

mmc:DeferredTaxAssetsTaxDeferredExpenseOtherNetOfValuationAllowance

mmc:DeferredTaxAssetsTaxDeferredExpenseReservesandAccrualsNetofValuationAllowance
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
mmc:DefinedBenefitPlanCumulativeEmployerContributionsInExcessOfNetPeriodicCost

mmc:DefinedContributionPlanEmployeeStockOwnershipPlanESOPSharesinESOPValue
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
mmc:EquityMethodInvestmentOwnershipPercentageSold
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:StatementScenario
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
mmc:FiduciaryAssetsFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument

mmc:FiduciaryLiabilitiesGrossNoncurrent

mmc:LiabilityForErrorsAndOmissions

mmc:PaymentofContingentConsideration

mmc:PaymentsForPreviousAcquisitionDeferredandContingentConsideration

mmc:StockholdersEquitySubtotalBeforeTreasuryStock

mmc:UncollectedPremiumsandClaimsNetofRelatedPayables

us-gaap:AccountsReceivableGrossCurrent
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType, us-gaap:StatementEquityComponents
us-gaap:AccumulatedOtherComprehensiveIncomeLossBeforeTax1

us-gaap:AdditionalPaidInCapitalCommonStock

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:AssetsFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest

us-gaap:CapitalizedComputerSoftwareAccumulatedAmortization

us-gaap:CapitalizedComputerSoftwareNet
us-gaap:CapitalizedContractCost
us-gaap:CapitalizedContractCostNet
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:CashAndCashEquivalentsFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

us-gaap:CommercialPaper

us-gaap:ContractWithCustomerAssetNet

us-gaap:ContractWithCustomerLiability
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
us-gaap:DebtInstrumentFaceAmount
us-gaap:BalanceSheetLocation, us-gaap:DebtInstrument, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:DebtInstrumentFairValue
us-gaap:BalanceSheetLocation, us-gaap:DebtInstrument, us-gaap:FairValueByMeasurementFrequency
us-gaap:DebtInstrument
us-gaap:DebtInstrumentUnusedBorrowingCapacityAmount
us-gaap:Range
us-gaap:DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible

us-gaap:DeferredIncomeTaxAssetsNet
us-gaap:BalanceSheetLocation

us-gaap:DeferredIncomeTaxLiabilities
us-gaap:BalanceSheetLocation
us-gaap:DeferredIncomeTaxLiabilitiesNet
us-gaap:IncomeTaxAuthority
us-gaap:DeferredTaxAssetsOperatingLossCarryforwards

us-gaap:DeferredTaxLiabilitiesDeferredExpense

us-gaap:DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals

us-gaap:DeferredTaxLiabilitiesOther

us-gaap:DeferredTaxLiabilitiesPropertyPlantAndEquipment

us-gaap:DeferredTaxLiabilitiesUndistributedForeignEarnings
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmountsRecognizedInBalanceSheet

us-gaap:DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedAmortizationNextFiscalYear
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
us-gaap:RetirementPlanName, us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear
us-gaap:RetirementPlanSponsorLocation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanFundedStatusOfPlan

us-gaap:DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanUltimateHealthCareCostTrendRate1
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanWeightedAverageAssetAllocations

us-gaap:DerivativeLiabilities

us-gaap:EmployeeRelatedLiabilitiesCurrent
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquityMethodInvestmentOwnershipPercentage

us-gaap:EquityMethodInvestments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:InvestmentType
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:EquitySecuritiesFvNi
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency
us-gaap:InvestmentType

us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValueAmount

us-gaap:EscrowDeposit

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
us-gaap:DefinedBenefitPlanByPlanAssetCategories
us-gaap:FairValueByLiabilityClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsGross
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:InterestRateFairValueHedgeAssetAtFairValue
us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:LiabilitiesFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency
us-gaap:CreditFacility, us-gaap:DebtInstrument
us-gaap:LineOfCredit
us-gaap:CreditFacility, us-gaap:SubsequentEventType
us-gaap:DebtInstrument
us-gaap:CreditFacility, us-gaap:DebtInstrument
us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity
us-gaap:CreditFacility, us-gaap:DebtInstrument, us-gaap:SubsequentEventType
us-gaap:DebtInstrument, us-gaap:SubsequentEventType
us-gaap:DebtInstrument
us-gaap:LinesOfCreditCurrent

us-gaap:LongTermDebtAndCapitalLeaseObligations
us-gaap:FairValueByMeasurementBasis
us-gaap:LongTermDebtFairValue

us-gaap:LossContingencyEstimateOfPossibleLoss

us-gaap:NumberOfCountriesInWhichEntityOperates

us-gaap:OperatingLeaseLiability

us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:OtherAssetsFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherIntangibleAssetsNet

us-gaap:OtherReceivablesGrossCurrent
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities

us-gaap:RestrictedCashAndCashEquivalentsAtCarryingValue
us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringAndRelatedCostCostIncurredToDate1

us-gaap:RestructuringReserve
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringCostAndReserve

us-gaap:RevenueRemainingPerformanceObligation
us-gaap:Subsegments
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
us-gaap:AwardType, us-gaap:PlanName
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
us-gaap:AwardType, us-gaap:PlanName
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:SharePrice

us-gaap:ShortTermBorrowings
us-gaap:DebtInstrument
us-gaap:ShortTermDebtType
us-gaap:FairValueByMeasurementBasis
us-gaap:ShorttermDebtFairValue

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
us-gaap:StatementEquityComponents

us-gaap:TreasuryStockShares

us-gaap:UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued

us-gaap:UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate

Tables

  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:CommonStockSharesOutstanding ▂▁▂▃▃▁▁▂▄▄▅▇█506504505507507504504505508509511513515
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding 510NA511512511NA510512514NA519520522
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic 505NA506507505NA504507508NA512514515
us-gaap:EarningsPerShareBasic █▄▄▄█▂▃▆▇▁▄▆▆1.490.770.60.661.420.30.551.051.360.060.770.981.1
us-gaap:EarningsPerShareDiluted █▄▄▄█▂▃▆▇▁▄▅▆1.480.760.590.651.40.30.541.041.340.060.760.961.09
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax █▆▄▆▅▃▂▃▅▃▁▂▂4651426439684349407137123504373440003685334134953503
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax dei:LegalEntity mmc:MarshMcLennanCompaniesInc.17000NANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems us-gaap:OperatingSegments█▆▄▆▅▃▂▃▅▃▁▂467342813991437440963730351937464012370133503508NA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,mmc:ConsultingSegment▅█▆▆▃▆▃▂▃▅▁▁176218851785180016731805165616501668173915871592NA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,mmc:RiskandInsuranceServicesSegment█▅▄▆▅▂▂▃▅▂▁▂291123962206257424231925186320962344196217631916NA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments,us-gaap:Subsegments us-gaap:OperatingSegments,mmc:ConsultingSegment,mmc:MercerConsultingGroup▆█▇▆▂▅▃▃▃▄▂▁125113261280126011551228117511581171119311491109NA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments,us-gaap:Subsegments us-gaap:OperatingSegments,mmc:ConsultingSegment,mmc:OliverWymanGroupConsultingGroup▅▇▄▆▅█▃▄▄▆▁▃511559505540518577481492497546438483NA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments,us-gaap:Subsegments us-gaap:OperatingSegments,mmc:RiskandInsuranceServicesSegment,mmc:GuyCarpenterReinsuranceGroup█▂▃▄▆▁▂▃▆▂▃▃835161283400670108220336641242273295NA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments,us-gaap:Subsegments us-gaap:OperatingSegments,mmc:RiskandInsuranceServicesSegment,mmc:MarshInsuranceGroup▇█▅▇▃▄▂▄▃▃▁▂207622351923217417531817164317601703172014901621NA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ProductOrService,us-gaap:StatementBusinessSegments mmc:Health,mmc:ConsultingSegment█▅▄▅▄▄▁▂▄486455441458442449415429442NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ProductOrService,us-gaap:StatementBusinessSegments mmc:Wealth,mmc:ConsultingSegment▆█▆▇▂▂▁▃▄592621592613543543525552565NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementBusinessSegments mmc:ConsultingSegment▄█▅▅▂▆▁▁▂176218851785180016731805165616501668NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementBusinessSegments mmc:RiskandInsuranceServicesSegment█▅▃▆▅▁▁▃▄291123962206257424231925186320962344NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementBusinessSegments,us-gaap:Subsegments mmc:ConsultingSegment,mmc:MercerConsultingGroup▅█▆▅▁▄▂▁▂125113261280126011551228117511581171NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementBusinessSegments,us-gaap:Subsegments mmc:ConsultingSegment,mmc:OliverWymanGroupConsultingGroup▃▇▃▅▄█▁▂▂511559505540518577481492497NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementBusinessSegments,us-gaap:Subsegments mmc:RiskandInsuranceServicesSegment,mmc:GuyCarpenterReinsuranceGroup█▁▃▄▆▁▂▃▆827152273392663102215332637NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementBusinessSegments,us-gaap:Subsegments mmc:RiskandInsuranceServicesSegment,mmc:MarshGuyCarpenter█▅▃▆▅▁▁▃▄288823712175254824001906184520812331NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementBusinessSegments,us-gaap:Subsegments mmc:RiskandInsuranceServicesSegment,mmc:MarshInsuranceGroup▆█▄▇▂▃▁▂▂206122191902215617371804163017491694NANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementGeographical,us-gaap:StatementBusinessSegments mmc:International,mmc:RiskandInsuranceServicesSegment██▄█▄▃▁▃108310728881059876812704808NANANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementGeographical,us-gaap:StatementBusinessSegments mmc:UnitedStatesandCanada,mmc:RiskandInsuranceServicesSegment978NANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:StatementGeographical,us-gaap:StatementBusinessSegments us-gaap:EMEA,mmc:RiskandInsuranceServicesSegment█▆▃▆▅▃▁▃754661536652633522441526NANANANANA
us-gaap:OperatingExpenses ▇█▇█▄▄▃▃▄▃▁▁▁3581367235013669313330912963304330922999274427312694
us-gaap:OperatingIncomeLoss █▂▁▃▆▃▂▄▆▄▃▄▅1070592467680938621541691908686597764809
 us-gaap:OperatingIncomeLoss us-gaap:ConsolidationItems us-gaap:OperatingSegments█▃▁▄▇▃▂▃▆▃▂▄▅11367015357951012677584739963737643811854
 us-gaap:OperatingIncomeLoss us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,mmc:ConsultingSegment▄█▇▄▄▅▅▃▁▇▇▄▁282336317278279294291267247321329283241
 us-gaap:OperatingIncomeLoss us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,mmc:RiskandInsuranceServicesSegment█▃▁▄▇▃▂▄▆▃▂▄▅854365218517733383293472716416314528613
us-gaap:InterestExpense ▇▇▇█▆▄▂▂▁▁▁▁▁1271301331411209269686159606058
us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax ▁█▃▆▆▆▄▃▇▆▆▇▇-930517-47515946-242-51622365126289235
us-gaap:IncomeLossFromContinuingOperations █▅▄▄█▂▃▆▇▁▅▆▆75439130333271615327653169027393501569
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest █▄▃▄▇▁▂▅▇▅▄▅▆1007531414550944224385719916642537711753
us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest █▄▄▄█▂▃▆▇▁▄▆▆76739630634472715927953669628397507578
us-gaap:IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity █▃▂▇▇▄▂▃▄▁▃▄▆1353121163561469
us-gaap:IncomeTaxExpenseBenefit ▃▂▂▃▃▁▂▃▃█▂▃▂24013510820621765106183220614140204175
us-gaap:IncomeTaxesPaidNet ▃█▂▆▃▅▁█▂136219115196131177106221128NANANANA
us-gaap:ProfitLoss █▄▄▄█▂▃▆▇▁▄▆▆76739630634472715927953669630397507578
 us-gaap:ProfitLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings█▄▄▄█▂▃▆▇▁▅▆▆75439130333271615327653169029393501569
us-gaap:ComprehensiveIncomeNetOfTax ▁▄▁▅▇▂▂▃█▆▅██-38267-101395773-653171842546374797825
us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest █▃▂▇▇▄▂▃▄▁▃▄▆1353121163561469
us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest ▂▄▁▅█▂▂▃█▆▅██-25272-98407784056176848547378803834
us-gaap:NetIncomeLoss █▄▄▄█▂▃▆▇▁▅▆▆75439130333271615327653169029393501569
us-gaap:NetIncomeLossAttributableToNoncontrollingInterest █▃▂▇▇▄▂▃▄▁▃▄▆1353121163561469
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:Assets ██▇█▇▂▂▂▂▂▁▁▁31391313573109732116301372157821129211592137920429196901944218969
us-gaap:LiabilitiesAndStockholdersEquity ██▇█▇▂▂▂▂▂▁▁▁31391313573109732116301372157821129211592137920429196901944218969
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:AssetsCurrent ▄▃▃▃█▂▂▂▂▂▁▁▁77497068705675261267559345966617562705562521551824981
us-gaap:CashAndCashEquivalentsAtCarryingValue █▄▅▆▃▃▁▂▄▄▃▁▁1480115512131294111710669511036116812051078966930
us-gaap:ReceivablesNetCurrent █▇▇█▄▃▄▄▄▂▁▂▁5558523651985553463043174476460145624133390939843795
us-gaap:OtherAssetsCurrent ██▇█▆▆▆▆▆▁▁▁▁711677645679569551539538540224228232256
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:PropertyPlantAndEquipmentGross NA2859NANANA2543NANANA2538NANANA
 us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:FurnitureAndFixturesNA1268NANANA1159NANANA1179NANANA
 us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:LandAndBuildingNA377NANANA377NANANA385NANANA
 us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:LeaseholdImprovementsNA1214NANANA1007NANANA974NANANA
us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment ██▆█▅▄▄▄▅▃▃▂▁2012200119442018188918421863185718891826182217581729
us-gaap:PropertyPlantAndEquipmentNet ██▆▅▂▁▁▁▂▂▂▂▂850858816799716701707698713712728721722
us-gaap:Goodwill ████▂▂▂▁▂▁▁▁▁14412146711428614479973995999435917791949089910088218769
 us-gaap:Goodwill us-gaap:StatementBusinessSegments mmc:ConsultingSegment█▇▇▆▄▄▂▃▃▂▂▁▁3100300030002900280028002600270027002600260025002500
 us-gaap:Goodwill us-gaap:StatementBusinessSegments mmc:RiskandInsuranceServicesSegment▇█▇█▂▂▂▁▁▁▁▁▁11300117001130011600690068006800650065006500650063006300
us-gaap:IntangibleAssetsNetExcludingGoodwill NA2774NANANA1437NANANA1274NANANA
us-gaap:FiniteLivedIntangibleAssetsNet ▆▇▇█▂▂▁▁▁▁▁▁▁2663277428693083146414371329123412561274132012331291
 us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass us-gaap:CustomerRelationships▆▇▇█▂▂▁▁▁▁▁▁▁2499259727022899136113311226113111401154119211281169
us-gaap:OtherAssetsNoncurrent ▅█▇█▄▅▃▅▅▄▁▅▂1519175716531764142315391381153515351430122515291325
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:LiabilitiesCurrent ██▇▇▆▄▃▂▂▂▁▁▁6859667962046382573949244727421641224262381436493588
us-gaap:DebtCurrent █▅▄▆▆▂▃▂▂▂▁▁▂2409121511391663156231463843951226213162412
us-gaap:LongTermDebtCurrent ▅█▄▆▆▃▄▂▂▂▁▁▂71612155148148143145632642632621312262
us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent ▇█▅▇▃▃▄▃▄▂▁▁▁2611274624792600224422342293224623432083200220272033
us-gaap:AccruedIncomeTaxesCurrent █▂▇▂█▁▂▅█▄▆▃▄256179251165256157179216261199229193202
us-gaap:DividendsPayableCurrent █▁██▇▁▇▇▇▁▇▇▆231023223221102112121930193194176
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:LongTermDebt ▁▁▁█11947119561194312273NA5824NANANANANANANA
 us-gaap:LongTermDebt us-gaap:DebtInstrument mmc:A4.90SeniorDebtObligationsDue2049███▁1237123712371236NA0NANANANANANANA
 us-gaap:LongTermDebt us-gaap:DebtInstrument mmc:SeniorDebtObligationsDue2029▄▄▄▄1499149914991499NA0NANANANANANANA
us-gaap:LongTermDebtNoncurrent ▆▁██11231107411142911459NA5510NANANANANANANA
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent ▇█▄▅▃▃▁▁▂▃▄▄▄2248233619982044187419111727176818421888194819862025
us-gaap:MinorityInterest ▄▄▅█▁▁▁▁▁▁▁▁▁156150177272777385818183858187
us-gaap:OtherLiabilitiesNoncurrent ▅▆▆█▄▅▅▄▄▅▂▁▁13611397138815941194136213221262126713111006949958
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:RetainedEarningsAccumulatedDeficit █▇▆▆▆▅▅▅▄▂▂▂▁15490151991481114741146421434714196141311381213140131131291512606
us-gaap:TreasuryStockValue ▇█▇▆▆▇▇▆▅▄▃▂▁3655377436173446338535673587344332103083285127052531
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▁▄▄▆▆▅▆▇██▆▆▅-5847-5055-4931-4527-4590-4647-4488-4265-3905-4043-4560-4541-4837
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▁██▆▂█▇▇▂▇▇▇▂-63810701050517-2761109906777-364756794742-399
us-gaap:NetCashProvidedByUsedInInvestingActivities ███▁██▇█████▇-245-167-74-5243-187-337-473-209-70-97-321-77-461
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▁▁▁█▂▂▂▃▂▂▂▃1340-1031-987-15026826-563-515-526294-482-543-681697
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▁██▆▂█▇▇▂▇▇▇▂-63810701050517-2761109906777-364756794742-399
us-gaap:NetIncomeLoss █▄▄▄█▂▃▆▇▁▅▆▆75439130333271615327653169029393501569
us-gaap:ProfitLoss █▄▄▄█▂▃▆▇▁▄▆▆76739630634472715927953669630397507578
 us-gaap:ProfitLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings█▄▄▄█▂▃▆▇▁▅▆▆75439130333271615327653169029393501569
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ███▁██▇█████▇-245-167-74-5243-187-337-473-209-70-97-321-77-461
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▆█▇▄▂▄▄▃▁▃▂▃▁11813712388739287775885738262
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▁▁▁█▂▂▂▃▂▂▂▃1340-1031-987-15026826-563-515-526294-482-543-681697
us-gaap:RepaymentsOfLongTermDebt █▅▅▇▁▅▁▁▁▁▂▄▁50330430345432534332572515
us-gaap:PaymentsForRepurchaseOfCommonStock NA18520010000175250250300200200200
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:RepaymentsOfLongTermDebt █▅▅▇▁▅▁▁▁▁▂▄▁50330430345432534332572515

Common Stock Value

Common Stock Par Or Stated Value Per Share

Common Stock Shares Issued

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-03-312008-12-312007-12-31
Value506504505507507504504505508509511513515514516519521522522531538540542546549547547549550545544544546539538541548541543542541530526517514520
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Authorized

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value510511512511510512514519520522523525526533541545551556556558559557552553551549555552548545536526515
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value505506507505504507508512514515518521521528535539544549548549551548544545542540547544543541533524515
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value1.490.770.60.661.420.30.551.051.360.060.770.981.10.850.730.910.920.720.610.780.890.540.550.780.810.550.460.710.750.440.60.640.240.510.590.30.430.460.410.33
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value1.480.760.590.651.40.30.541.041.340.060.760.961.090.840.730.90.910.710.610.770.880.540.540.770.80.540.450.690.740.440.590.630.240.50.580.30.430.450.410.33
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Income Loss From Continuing Operations Per Basic Share

Income Loss From Continuing Operations Per Diluted Share

Revenue From Contract With Customer Excluding Assessed Tax

Revenue From Contract With Customer Including Assessed Tax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value4651426439684349407137123504373440003685334134953503
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

mmc:MarshMcLennanCompaniesInc.



Period End2020-03-31
Value17000
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax365.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax365.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:MarshMcLennanCompaniesInc.100.0

us-gaap:ConsolidationItems

mmc:CorporateAndEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-22-17-23-25-25-18-15-12-12-16-9-13
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.5-0.4-0.6-0.6-0.6-0.5-0.4-0.3-0.3-0.4-0.3-0.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.5-0.4-0.6-0.6-0.6-0.5-0.4-0.3-0.3-0.4-0.3-0.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:CorporateAndEliminations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value467342813991437440963730351937464012370133503508
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.5100.4100.6100.6100.6100.5100.4100.3100.3100.4100.3100.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.5100.4100.6100.6100.6100.5100.4100.3100.3100.4100.3100.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:IntersegmentElimination, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value2116202224171112111689
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.50.40.50.50.60.50.30.30.30.40.20.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.50.40.50.50.60.50.30.30.30.40.20.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:IntersegmentElimination mmc:ConsultingSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IntersegmentElimination, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value113311401014
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.00.10.10.00.00.10.00.00.00.00.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.00.10.10.00.00.10.00.00.00.00.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:IntersegmentElimination mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.0

us-gaap:OperatingSegments, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value176218851785180016731805165616501668173915871592
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax37.944.245.041.441.148.647.344.241.747.247.545.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax37.944.245.041.441.148.647.344.241.747.247.545.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:ConsultingSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value291123962206257424231925186320962344196217631916
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax62.656.255.659.259.551.953.256.158.653.252.854.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax62.656.255.659.259.551.953.256.158.653.252.854.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments, us-gaap:Subsegments

us-gaap:OperatingSegments, mmc:ConsultingSegment, mmc:MercerConsultingGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value125113261280126011551228117511581171119311491109
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax26.931.132.329.028.433.133.531.029.332.434.431.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax26.931.132.329.028.433.133.531.029.332.434.431.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:ConsultingSegment mmc:MercerConsultingGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, mmc:ConsultingSegment, mmc:OliverWymanGroupConsultingGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value511559505540518577481492497546438483
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax11.013.112.712.412.715.513.713.212.414.813.113.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax11.013.112.712.412.715.513.713.212.414.813.113.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:ConsultingSegment mmc:OliverWymanGroupConsultingGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment, mmc:GuyCarpenterReinsuranceGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value835161283400670108220336641242273295
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax18.03.87.19.216.52.96.39.016.06.68.28.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax18.03.87.19.216.52.96.39.016.06.68.28.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:RiskandInsuranceServicesSegment mmc:GuyCarpenterReinsuranceGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment, mmc:MarshInsuranceGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value207622351923217417531817164317601703172014901621
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax44.652.448.550.043.148.946.947.142.646.744.646.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax44.652.448.550.043.148.946.947.142.646.744.646.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:RiskandInsuranceServicesSegment mmc:MarshInsuranceGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

mmc:Career, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value173250247189170236235177164
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax3.75.96.24.34.26.46.74.74.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax3.75.96.24.34.26.46.74.74.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:Career mmc:ConsultingSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:Health, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value486455441458442449415429442
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax10.410.711.110.510.912.111.811.511.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax10.410.711.110.510.912.111.811.511.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:Health mmc:ConsultingSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:Wealth, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value592621592613543543525552565
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.714.614.914.113.314.615.014.814.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.714.614.914.113.314.615.014.814.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:Wealth mmc:ConsultingSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments

mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value176218851785180016731805165616501668
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax37.944.245.041.441.148.647.344.241.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax37.944.245.041.441.148.647.344.241.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:ConsultingSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value291123962206257424231925186320962344
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax62.656.255.659.259.551.953.256.158.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax62.656.255.659.259.551.953.256.158.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments, us-gaap:Subsegments

mmc:ConsultingSegment, mmc:MercerConsultingGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value125113261280126011551228117511581171
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax26.931.132.329.028.433.133.531.029.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax26.931.132.329.028.433.133.531.029.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:ConsultingSegment mmc:MercerConsultingGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:ConsultingSegment, mmc:OliverWymanGroupConsultingGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value511559505540518577481492497
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax11.013.112.712.412.715.513.713.212.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax11.013.112.712.412.715.513.713.212.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:ConsultingSegment mmc:OliverWymanGroupConsultingGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:RiskandInsuranceServicesSegment, mmc:GuyCarpenterReinsuranceGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value827152273392663102215332637
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax17.83.66.99.016.32.76.18.915.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax17.83.66.99.016.32.76.18.915.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:RiskandInsuranceServicesSegment mmc:GuyCarpenterReinsuranceGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:RiskandInsuranceServicesSegment, mmc:MarshGuyCarpenter



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value288823712175254824001906184520812331
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax62.155.654.858.659.051.352.755.758.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax62.155.654.858.659.051.352.755.758.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:RiskandInsuranceServicesSegment mmc:MarshGuyCarpenter100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:RiskandInsuranceServicesSegment, mmc:MarshInsuranceGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value206122191902215617371804163017491694
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax44.352.047.949.642.748.646.546.842.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax44.352.047.949.642.748.646.546.842.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:RiskandInsuranceServicesSegment mmc:MarshInsuranceGroup100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementGeographical, us-gaap:StatementBusinessSegments

mmc:International, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value108310728881059876812704808
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax23.325.122.424.421.521.920.121.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax23.325.122.424.421.521.920.121.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:International mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.0100.0

mmc:UnitedStatesandCanada, mmc:RiskandInsuranceServicesSegment



Period End2020-03-31
Value978
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax21.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax21.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:UnitedStatesandCanada mmc:RiskandInsuranceServicesSegment100.0

srt:AsiaPacific, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value238255242291165169167183
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.16.06.16.74.14.64.84.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.16.06.16.74.14.64.84.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax srt:AsiaPacific mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.0100.0

srt:LatinAmerica, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value91156110116781219699
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.03.72.82.71.93.32.72.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.03.72.82.71.93.32.72.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax srt:LatinAmerica mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EMEA, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value754661536652633522441526
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.215.513.515.015.514.112.614.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.215.513.515.015.514.112.614.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:EMEA mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.0100.0

Operating Expenses

us-gaap:OperatingExpenses



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value358136723501366931333091296330433092299927442731269427312563265026032744265425962480271026962653259125282511251924672508252424962463241222852656235621592285
Percentage of OperatingExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax77.086.188.284.477.083.384.681.577.381.482.178.176.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Operating Income Loss

us-gaap:OperatingIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value1070592467680938621541691908686597764809633572726733594461629735536445647673489404577607406378518527310465472239-50439195324
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax23.013.911.815.623.016.715.418.522.718.617.921.923.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

mmc:CorporateAndEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-30
Value-66-109-68-115-74-56-43-48-55-51-46-47-45-45-51-49-47-54-49-46
Percentage of OperatingIncomeLoss-6.2-18.4-14.6-16.9-7.9-9.0-7.9-6.9-6.1-7.4-7.7-6.2-5.6-7.1-8.9-6.7-6.4-9.1-10.6-7.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.4-2.6-1.7-2.6-1.8-1.5-1.2-1.3-1.4-1.4-1.4-1.3-1.30.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax mmc:CorporateAndEliminations300.0641.2295.7460.0296.0311.1286.7400.0458.3318.8511.1361.50.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value11367015357951012677584739963737643811854678623775780648510675781589503695718454626655427
Percentage of OperatingIncomeLoss106.2118.4114.6116.9107.9109.0107.9106.9106.1107.4107.7106.2105.6107.1108.9106.7106.4109.1110.6107.3106.3109.9113.0107.4106.7112.4108.5107.9113.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax24.416.413.518.324.918.216.719.824.120.019.223.224.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments24.316.413.418.224.718.216.619.724.019.919.223.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value282336317278279294291267247321329283241265308285245294285248248250274247225232205187205
Percentage of OperatingIncomeLoss26.456.867.940.929.747.353.838.627.246.855.137.029.841.953.839.333.449.561.839.433.746.661.638.233.457.435.530.854.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.17.98.06.46.97.98.37.26.28.79.88.16.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:ConsultingSegment16.017.817.815.416.716.317.616.214.818.520.717.80.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value854365218517733383293472716416314528613413315490535354225427533339229448493222421468222
Percentage of OperatingIncomeLoss79.861.746.776.078.161.754.268.378.960.652.669.175.865.255.167.573.059.648.867.972.563.251.569.273.355.073.077.158.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax18.48.65.511.918.010.38.412.617.911.39.415.117.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments mmc:RiskandInsuranceServicesSegment29.315.29.920.130.319.915.722.530.521.217.827.60.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.00.00.00.00.00.0-1000000.00.00.0-1000000.00.00.00.0
Percentage of OperatingIncomeLoss0.00.00.00.00.00.0-0.20.00.0-0.10.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.00.00.00.00.0-0.00.00.0-0.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OtherPostretirementBenefitPlansDefinedBenefit0.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-8-3-10-10-8-9-87-10-20-1919-18
Percentage of OperatingIncomeLoss-0.7-0.5-2.1-1.5-0.9-1.4-1.51.0-1.1-2.9-3.22.5-2.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.2-0.1-0.3-0.2-0.2-0.2-0.20.2-0.2-0.5-0.60.5-0.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:PensionPlansDefinedBenefit0.00.00.00.00.00.00.00.00.00.00.00.00.0

Interest Expense

us-gaap:InterestExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value12713013314112092696861596060584847484646414036364542424040444445464949516060605956
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.73.03.43.22.92.52.01.81.51.61.81.71.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-930517-47515946-242-51622365126289235-404-54-33313-187-276243-423-311-41913778256-84-256167-177162
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-20.012.1-12.00.32.30.2-6.9-13.85.61.83.88.36.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations

us-gaap:IncomeLossFromContinuingOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value75439130333271615327653169027393501569436379472481374321419485264298433444254393401240
Percentage of IncomeLossFromContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.29.27.67.617.64.17.914.217.20.711.814.316.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-31
Value1007531414550944224385719916642537711753588525681686551457595704368432608649383564588336483507198415447
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax21.712.510.412.623.26.011.019.322.917.416.120.321.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value76739630634472715927953669628397507578441384480490380329429498269305440457307260400412246339354133286319128-29274207179
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.59.37.77.917.94.38.014.417.40.811.914.516.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations Before Income Taxes Domestic

Income Loss From Continuing Operations Before Income Taxes Foreign

Income Loss From Continuing Operations Attributable To Noncontrolling Entity

us-gaap:IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value135312116356146955896810135771367116
Percentage of IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.10.10.30.30.20.10.10.10.00.10.20.30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value2401351082062176510618322061414020417514714120119617112816620699127168192123164176901441536512912855-60117-4680
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.23.22.74.75.31.83.04.95.516.74.25.85.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Taxes Paid Net

us-gaap:IncomeTaxesPaidNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value136219115196131177106221128
Percentage of IncomeTaxesPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.95.12.94.53.24.83.05.93.2

Profit Loss

us-gaap:ProfitLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value76739630634472715927953669630397507578441384480490381331429495299304438456259395424247337354135289331171242252225180
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.59.37.77.917.94.38.014.417.40.811.914.516.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value132826121163561469558968101357713711
Percentage of ProfitLoss1.77.18.53.51.53.81.10.90.93.31.01.21.61.11.31.71.81.62.42.32.61.72.31.62.91.82.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.70.70.30.30.20.10.10.10.00.10.20.30.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value75439130333271615327653169029393501569436379472481375323419482294297431443388413
Percentage of ProfitLoss98.398.799.096.598.596.298.999.199.196.799.098.898.498.998.798.398.298.497.697.797.498.397.798.497.198.297.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.29.27.67.617.64.17.914.217.20.811.814.316.20.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-03-31
Value-38267-101395773-653171842546374797825-368391268604277124586239-6589532356475332341351237512-125387442173
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.86.3-2.59.119.0-0.21.54.621.114.811.222.823.60.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-03-31
Value135312116356146955896810135771367116875764
Percentage of ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.10.10.30.30.20.10.10.10.00.10.20.30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-03-312009-03-31
Value-25272-98407784056176848547378803834-363396276613283132596252-65316539369481339352357245519-120394448177146
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.56.4-2.59.419.30.01.64.721.214.811.323.023.80.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value75439130333271615327653169029393501569436379472481375323419482294297431443303253388413241329347130282325168236248221176
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.29.27.67.617.64.17.914.217.20.811.814.316.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss Available To Common Stockholders Basic

Net Income Loss Available To Common Stockholders Diluted

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value1353121163561469558968101357713671168757636444
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.10.10.30.30.20.10.10.10.00.10.20.30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Assets

us-gaap:Assets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value313913135731097321163013721578211292115921379204291969019442189691819018358180761812818216177241741316834178401798717588165771698016976158381553716288157361520215010154541512115451150731531014903149621533715206
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems

mmc:CorporateAndEliminations



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value-4463-2293-4261-3308-1559-334
Percentage of Assets-14.2-10.6-20.9-18.2-8.6-1.9
Percentage of Assets-14.2-10.6-20.9-18.2-8.6-1.9
Percentage of Assets mmc:CorporateAndEliminations100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value358202387124690214981977518127165431503513922
Percentage of Assets114.2110.6120.9118.2108.6101.697.492.390.1
Percentage of Assets114.2110.6120.9118.2108.6101.697.492.390.1
Percentage of Assets us-gaap:OperatingSegments100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, mmc:ConsultingSegment



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value972280038200677064855916517852034820
Percentage of Assets31.037.140.137.235.633.230.531.931.2
Percentage of Assets31.037.140.137.235.633.230.531.931.2
Percentage of Assets us-gaap:OperatingSegments mmc:ConsultingSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value2609815868164901472813290122111136598329102
Percentage of Assets83.273.580.781.073.068.466.960.458.9
Percentage of Assets83.273.580.781.073.068.466.960.458.9
Percentage of Assets us-gaap:OperatingSegments mmc:RiskandInsuranceServicesSegment100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value313913135731097321163013721578211292115921379204291969019442189691819018358180761812818216177241741316834178401798717588165771698016976158381553716288157361520215010154541512115451150731531014903149621533715206
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

Assets Current

us-gaap:AssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value7749706870567526126755934596661756270556252155182498148845209493047985044552652995177605568526414556363006161521450975963565151955035564850305186493652765045459249314784
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets24.722.522.723.442.127.528.229.229.327.226.526.726.326.828.427.326.527.731.230.430.833.938.136.533.637.136.332.932.836.635.934.233.536.533.333.632.734.533.930.732.231.5

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-03-312008-12-312007-12-312006-12-31
Value14801155121312941117106695110361168120510789669301026138897491813741330930110419582649200513802303217412301263230120441504141021131714165913301894169515101167177718131414168521332089
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.73.73.94.03.74.94.54.95.55.95.55.04.95.67.65.45.17.57.55.36.611.014.711.48.313.612.87.88.114.113.09.99.413.711.310.78.812.411.40.07.811.60.00.011.10.00.0

Short Term Investments

Receivables Net Current

us-gaap:ReceivablesNetCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value5558523651985553463043174476460145624201413339093984379536433603372136473471351736593380337734963706346233103294334531763058305931023008290629253111321230353055293528552755
Percentage of ReceivablesNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets17.716.716.717.315.420.021.221.721.30.020.219.920.520.020.019.620.620.119.119.821.020.118.919.421.120.919.519.421.120.418.819.420.420.018.819.320.121.319.820.519.618.618.1

Other Assets Current

us-gaap:OtherAssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value711677645679569551539538540542224228232256215218235233199213235227199229223237205234229222194214208227253391416394347295490299344
Percentage of OtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.32.22.12.11.92.62.62.52.50.01.11.21.21.31.21.21.31.31.11.21.31.31.11.31.31.41.21.41.41.41.21.41.41.51.62.62.72.62.32.03.31.92.3

Property Plant And Equipment Gross

us-gaap:PropertyPlantAndEquipmentGross



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value28592543253824082394244824252391227322332182
Percentage of PropertyPlantAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets9.111.812.413.213.113.714.314.714.714.614.2

us-gaap:PropertyPlantAndEquipmentByType

us-gaap:FurnitureAndFixtures



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value1268115911791113113311931201116811011079
Percentage of PropertyPlantAndEquipmentGross44.445.646.546.247.348.749.548.848.448.3
Percentage of Assets4.05.45.86.16.26.77.17.27.17.0
Percentage of Assets us-gaap:FurnitureAndFixtures0.00.00.00.00.00.00.00.00.00.0

us-gaap:LandAndBuilding



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value377377385389396401408412405402
Percentage of PropertyPlantAndEquipmentGross13.214.815.216.216.516.416.817.217.818.0
Percentage of Assets1.21.71.92.12.22.22.42.52.62.6
Percentage of Assets us-gaap:LandAndBuilding0.00.00.00.00.00.00.00.00.00.0

us-gaap:LeaseholdImprovements



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value12141007974906865854816811767752
Percentage of PropertyPlantAndEquipmentGross42.539.638.437.636.134.933.633.933.733.7
Percentage of Assets3.94.74.85.04.74.84.85.05.04.9
Percentage of Assets us-gaap:LeaseholdImprovements0.00.00.00.00.00.00.00.00.00.0

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-31
Value20122001194420181889184218631857188918261822175817291683169416661651162116571663163516391655166316161597161115951586158215511535153514691483136614611411141114771465
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.46.46.36.36.38.58.88.88.88.99.39.09.19.39.29.29.18.99.39.69.79.29.29.59.79.49.510.110.29.79.910.110.29.59.88.89.79.29.59.99.6

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value850858816799716701707698713712728721722725717736757773786807794809822843825828824804793809807800795804804823828822816920952969
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.72.72.62.52.43.23.33.33.33.53.73.73.84.03.94.14.24.24.44.64.74.54.64.85.04.94.95.15.15.05.15.35.35.25.35.35.55.45.56.16.26.4

us-gaap:StatementGeographical

country:GB



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value149919194115120121121133
Percentage of PropertyPlantAndEquipmentNet17.413.012.813.014.914.814.615.016.5
Percentage of Assets0.50.40.40.50.60.70.70.70.9
Percentage of Assets country:GB0.00.00.00.00.00.00.00.00.0

country:US



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value462403399412460483494494505
Percentage of PropertyPlantAndEquipmentNet53.857.556.056.859.559.759.761.162.8
Percentage of Assets1.51.92.02.32.52.72.93.03.3
Percentage of Assets country:US0.00.00.00.00.00.00.00.00.0

mmc:OtherGeographicAreas



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value7874879092847769646773
Percentage of PropertyPlantAndEquipmentNet9.110.612.212.411.910.49.38.58.08.27.7
Percentage of Assets0.20.30.40.50.50.50.50.40.40.40.5
Percentage of Assets mmc:OtherGeographicAreas0.00.00.00.00.00.00.00.00.00.00.0

srt:AsiaPacific



Period End2019-12-312018-12-312017-12-312016-12-31
Value101747876
Percentage of PropertyPlantAndEquipmentNet11.810.611.010.5
Percentage of Assets0.30.30.40.4
Percentage of Assets srt:AsiaPacific0.00.00.00.0

srt:Europe



Period End2019-12-312018-12-312017-12-312016-12-31
Value68595753
Percentage of PropertyPlantAndEquipmentNet7.98.48.07.3
Percentage of Assets0.20.30.30.3
Percentage of Assets srt:Europe0.00.00.00.0

Long Term Investments

Goodwill

us-gaap:Goodwill



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value14412146711428614479973995999435917791949089910088218769836979757945795078897506738171607241717972307159689368656804675267926679664366756562653965956557642062866157608567816825
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets45.946.845.945.132.344.544.743.443.044.546.245.446.246.043.444.043.943.342.342.442.540.639.941.143.240.640.443.043.541.742.443.744.542.543.242.743.541.942.20.040.744.244.9

us-gaap:BusinessAcquisition

mmc:CurrentFiscalPeriodAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value1424962489597626410116155515333703635567462617833561881247235033426711393
Percentage of Goodwill1.034.733.81.06.54.31.30.26.15.94.24.16.60.90.80.89.94.72.50.26.54.94.63.71.61.4
Percentage of Assets0.516.015.20.32.91.90.50.12.72.71.91.93.10.40.30.34.32.01.10.12.61.91.91.60.70.5
Percentage of Assets mmc:CurrentFiscalPeriodAcquisitions0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value491247614695
Percentage of Goodwill33.533.332.4
Percentage of Assets15.715.314.6
Percentage of Assets mmc:JardineLloydThompsonGroupplc0.00.00.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value212201200
Percentage of Goodwill1.41.41.4
Percentage of Assets0.70.60.6
Percentage of Assets mmc:OtherAcquisitions0.00.00.0

mmc:TotalAcquisitions



Period End2019-12-31
Value5124
Percentage of Goodwill34.9
Percentage of Assets16.3
Percentage of Assets mmc:TotalAcquisitions0.0

us-gaap:StatementBusinessSegments

mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value310030003000290028002800260027002700260026002500250025002300230023002300220022002200220022002200220022002200
Percentage of Goodwill21.520.421.020.028.829.227.629.429.428.628.628.328.529.928.828.928.929.229.329.830.730.430.630.430.731.932.0
Percentage of Assets9.99.69.69.09.313.012.312.812.612.713.212.913.213.712.512.712.712.612.412.613.112.312.212.513.313.013.0
Percentage of Assets mmc:ConsultingSegment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value1130011700113001160069006800680065006500650065006300630059005700560057005600530052005000500050005000490047004700
Percentage of Goodwill78.479.779.180.170.870.872.170.870.771.571.471.471.870.571.570.571.771.070.670.569.869.169.669.268.468.268.5
Percentage of Assets36.037.336.336.122.931.532.230.730.431.833.032.433.232.431.031.031.430.729.929.929.728.027.828.429.627.727.7
Percentage of Assets mmc:RiskandInsuranceServicesSegment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Intangible Assets Net Excluding Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value27741437127411261036692
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0100.0100.0100.0
Percentage of Assets8.86.76.26.25.73.9

Finite Lived Intangible Assets Net

us-gaap:FiniteLivedIntangibleAssetsNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302009-12-31
Value2663277428693083146414371329123412561274132012331291112690795510351036836774672692635641640472488477447469434443454401394405436403361229
Percentage of FiniteLivedIntangibleAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets8.58.89.29.64.96.76.35.85.96.26.76.36.86.24.95.35.75.74.74.44.03.93.53.63.92.82.93.02.92.92.82.93.02.62.62.62.92.62.41.5

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CustomerLists



Period End2019-12-312018-12-312017-12-312016-12-312016-06-302016-03-312015-12-312014-12-31
Value259713311154998870940934609
Percentage of FiniteLivedIntangibleAssetsNet93.692.690.688.691.190.890.288.0
Percentage of Assets8.36.25.65.54.85.25.13.4
Percentage of Assets us-gaap:CustomerLists0.00.00.00.00.00.00.00.0

us-gaap:CustomerRelationships



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value2499259727022899136113311226113111401154119211281169998831934
Percentage of FiniteLivedIntangibleAssetsNet93.893.694.294.093.092.692.291.790.890.690.391.590.588.691.690.2
Percentage of Assets8.08.38.79.04.56.25.85.35.35.66.15.86.25.54.55.1
Percentage of Assets us-gaap:CustomerRelationships0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-31
Value16417716718410310610310311612012810512212876859510283
Percentage of FiniteLivedIntangibleAssetsNet6.26.45.86.07.07.47.88.39.29.49.78.59.511.48.48.99.29.812.0
Percentage of Assets0.50.60.50.60.30.50.50.50.50.60.70.50.60.70.40.50.50.60.5
Percentage of Assets us-gaap:OtherIntangibleAssets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Intangible Assets Net Including Goodwill

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value15191757165317641423153913811535153516561430122515291325121312121220129011771221121912091200976934937882838742739772748828841795793914881919903964945994
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.85.65.35.54.77.16.57.37.20.07.06.27.97.06.76.66.77.16.56.97.07.26.75.45.35.75.24.94.74.84.74.85.45.65.15.25.95.86.06.16.46.26.5

Liabilities Current

us-gaap:LiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value685966796204638257394924472742164122426238143649358840823825350431593708340432082753370541303530334338093893296428403564350631703032373933843242288931052947317437033386
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets21.921.320.019.919.022.822.419.919.320.919.418.818.922.420.819.417.420.419.218.416.420.823.020.120.222.422.918.718.321.922.320.920.224.222.421.019.220.319.821.224.122.3

Debt Current

us-gaap:DebtCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value240912151139166315623146384395122621316241231226226126512621116111640333432334
Percentage of DebtCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.73.93.75.25.21.53.02.12.41.30.10.82.21.71.41.41.50.10.30.60.40.13.61.92.62.0

Long Term Debt Current

us-gaap:LongTermDebtCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-07-152011-06-302011-03-312010-12-312010-09-302009-12-31
Value71612155148148143145632642632621312262262262261131262616111640333332334583101026025925925926026060026026189558
Percentage of LongTermDebtCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.33.91.72.52.71.52.71.21.21.30.10.11.41.41.41.40.10.10.30.40.40.13.61.92.02.03.40.10.11.61.61.71.71.71.70.01.71.70.10.13.6

Accounts Payable And Accrued Liabilities Current

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value26112746247926002244223422932246234322052083200220272033196918621868187918861759174816991883180018491895186118301721
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets8.38.88.08.17.410.410.910.611.00.010.210.210.410.710.810.110.310.410.49.910.010.110.610.010.511.411.010.810.6

Accrued Income Taxes Current

us-gaap:AccruedIncomeTaxesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value2561792511652561571792162611992291932021462131821281541072091361781992091761481481711481101541118063801104962066
Percentage of AccruedIncomeTaxesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0
Percentage of Assets0.80.60.80.50.80.70.81.01.21.01.21.01.10.81.21.00.70.80.61.20.81.01.11.21.10.90.91.11.00.71.00.70.50.40.50.70.30.40.00.4

Dividends Payable Current

us-gaap:DividendsPayableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302010-12-31
Value23102322322110211212193019319417601781781630163166151015315413901381391281261261211190
Percentage of DividendsPayableCurrent100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets0.70.00.70.70.70.01.01.00.90.01.01.00.90.01.01.00.90.00.91.00.90.00.90.90.80.00.80.90.80.80.80.80.80.0

Long Term Debt

us-gaap:LongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312014-12-31
Value1194711956119431227358243368
Percentage of LongTermDebt100.0100.0100.0100.0100.0100.0
Percentage of Assets38.138.138.438.227.018.9

us-gaap:DebtInstrument

mmc:A1.349SeniorDebtObligationsDue2026



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value6056096036180
Percentage of LongTermDebt5.15.15.05.00.0
Percentage of Assets1.91.91.91.90.0
Percentage of Assets mmc:A1.349SeniorDebtObligationsDue20260.00.00.00.00.0

mmc:A1.979SeniorDebtObligationsDue2030



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value6046076026170
Percentage of LongTermDebt5.15.15.05.00.0
Percentage of Assets1.91.91.91.90.0
Percentage of Assets mmc:A1.979SeniorDebtObligationsDue20300.00.00.00.00.0

mmc:A2.35SeniorDebtObligationsDue2019



Period End2019-12-312019-09-302019-06-302018-12-31
Value00300300
Percentage of LongTermDebt0.00.02.45.2
Percentage of Assets0.00.00.91.4
Percentage of Assets mmc:A2.35SeniorDebtObligationsDue20190.00.00.00.0

mmc:A3.50SeniorDebtObligationsDue2020



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value6996986986970
Percentage of LongTermDebt5.95.85.85.70.0
Percentage of Assets2.22.22.22.20.0
Percentage of Assets mmc:A3.50SeniorDebtObligationsDue20200.00.00.00.00.0

mmc:A3.50SeniorDebtObligationsDue2025



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value497497497497496
Percentage of LongTermDebt4.24.24.24.08.5
Percentage of Assets1.61.61.61.52.3
Percentage of Assets mmc:A3.50SeniorDebtObligationsDue20250.00.00.00.00.0

mmc:A3.75SeniorDebtObligationsDue2026



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value597597597597596
Percentage of LongTermDebt5.05.05.04.910.2
Percentage of Assets1.91.91.91.92.8
Percentage of Assets mmc:A3.75SeniorDebtObligationsDue20260.00.00.00.00.0

mmc:A3.875SeniorDebtObligationsDue2024



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value9949949939930
Percentage of LongTermDebt8.38.38.38.10.0
Percentage of Assets3.23.23.23.10.0
Percentage of Assets mmc:A3.875SeniorDebtObligationsDue20240.00.00.00.00.0

mmc:A4.75SeniorDebtObligationsDue2039



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value4944944944940
Percentage of LongTermDebt4.14.14.14.00.0
Percentage of Assets1.61.61.61.50.0
Percentage of Assets mmc:A4.75SeniorDebtObligationsDue20390.00.00.00.00.0

mmc:A4.90SeniorDebtObligationsDue2049



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value12371237123712360
Percentage of LongTermDebt10.410.310.410.10.0
Percentage of Assets3.93.94.03.80.0
Percentage of Assets mmc:A4.90SeniorDebtObligationsDue20490.00.00.00.00.0

mmc:A500MillionTwoYearTermLoanFacility



Period End2020-03-312019-12-31
Value5000
Percentage of LongTermDebt4.20.0
Percentage of Assets1.60.0
Percentage of Assets mmc:A500MillionTwoYearTermLoanFacility0.00.0

mmc:FloatingRateSeniorDebtObligationsDue2021



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value2992982982980
Percentage of LongTermDebt2.52.52.52.40.0
Percentage of Assets1.01.01.00.90.0
Percentage of Assets mmc:FloatingRateSeniorDebtObligationsDue20210.00.00.00.00.0

mmc:MortgageDue2035



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value341345347351358
Percentage of LongTermDebt2.92.92.92.96.1
Percentage of Assets1.11.11.11.11.7
Percentage of Assets mmc:MortgageDue20350.00.00.00.00.0

mmc:OtherDebtInstruments



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value67544
Percentage of LongTermDebt0.10.10.00.00.1
Percentage of Assets0.00.00.00.00.0
Percentage of Assets mmc:OtherDebtInstruments0.00.00.00.00.0

mmc:SeniorDebtObligationDue2047



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value493492492492492
Percentage of LongTermDebt4.14.14.14.08.4
Percentage of Assets1.61.61.61.52.3
Percentage of Assets mmc:SeniorDebtObligationDue20470.00.00.00.00.0

mmc:SeniorDebtObligations3.30Due2023



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value349349348348348
Percentage of LongTermDebt2.92.92.92.86.0
Percentage of Assets1.11.11.11.11.6
Percentage of Assets mmc:SeniorDebtObligations3.30Due20230.00.00.00.00.0

mmc:SeniorDebtObligationsDue2020



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value0500500499499
Percentage of LongTermDebt0.04.24.24.18.6
Percentage of Assets0.01.61.61.62.3
Percentage of Assets mmc:SeniorDebtObligationsDue20200.00.00.00.00.0

mmc:SeniorDebtObligationsDue2022



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value498498498498497
Percentage of LongTermDebt4.24.24.24.18.5
Percentage of Assets1.61.61.61.62.3
Percentage of Assets mmc:SeniorDebtObligationsDue20220.00.00.00.00.0

mmc:SeniorDebtObligationsDue2029



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value14991499149914990
Percentage of LongTermDebt12.512.512.612.20.0
Percentage of Assets4.84.84.84.70.0
Percentage of Assets mmc:SeniorDebtObligationsDue20290.00.00.00.00.0

mmc:SeniorDebtObligationsDue2033



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value298298298298297
Percentage of LongTermDebt2.52.52.52.45.1
Percentage of Assets0.91.01.00.91.4
Percentage of Assets mmc:SeniorDebtObligationsDue20330.00.00.00.00.0

Long Term Debt Noncurrent

us-gaap:LongTermDebtNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value112311074111429114595510
Percentage of LongTermDebtNoncurrent100.0100.0100.0100.0100.0
Percentage of Assets35.834.336.835.725.5

Deferred Tax Liabilities Noncurrent

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value22482336199820441874191117271768184218881948198620252076196920042042205821142072207022441094112311351150197519791993209415941574160616551148117812201211945116311841217
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.27.46.46.46.28.98.28.48.69.29.910.210.711.410.711.111.311.311.911.912.312.66.16.46.86.811.612.512.812.910.110.410.710.77.67.68.17.96.37.87.78.0

dei:LegalEntity

mmc:JardineLloydThompsonGroupplc



Period End2019-12-31
Value255
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent10.9
Percentage of Assets0.8
Percentage of Assets mmc:JardineLloydThompsonGroupplc0.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value282932
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent1.21.51.7
Percentage of Assets0.10.10.2
Percentage of Assets country:US us-gaap:OtherPostretirementBenefitPlansDefinedBenefit0.00.00.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value157814391407
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent67.675.374.5
Percentage of Assets5.06.76.9
Percentage of Assets country:US us-gaap:PensionPlansDefinedBenefit0.00.00.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value58546478
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent2.52.83.43.8
Percentage of Assets0.20.30.30.4
Percentage of Assets us-gaap:ForeignPlan us-gaap:OtherPostretirementBenefitPlansDefinedBenefit0.00.00.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value634345343414
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent27.118.118.219.9
Percentage of Assets2.01.61.72.3
Percentage of Assets us-gaap:ForeignPlan us-gaap:PensionPlansDefinedBenefit0.00.00.00.0

Minority Interest

us-gaap:MinorityInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value1561501772727773858181838581878083819289958991798277827078677364707167575853584745373538
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.50.50.60.80.30.30.40.40.40.40.40.40.50.40.50.40.50.50.50.50.50.40.50.40.50.40.50.40.50.40.40.50.40.40.40.30.40.30.30.20.20.2

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value136113971388159411941362132212621267133413111006949958957999104510891128108310799861041111411291083105298590685390692098597198410081027105411231127106210351137
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.34.54.55.04.06.36.36.05.90.06.45.14.95.15.35.45.86.06.26.16.25.95.86.26.46.56.25.85.75.55.65.86.56.56.46.76.67.07.37.67.16.77.5

Stockholders Equity

Common Stock Value

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value1549015199148111474114642143471419614131138121350413140131131291512606123881195311751114601130210928107681051510335100429897962094529151903687868628837182578053794976967688752874367236706270337237
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets49.348.547.645.948.666.567.266.864.60.064.366.666.466.568.165.165.063.262.061.761.862.557.955.856.358.055.753.957.156.553.053.254.353.751.450.949.849.948.648.647.245.947.6

Treasury Stock Value

us-gaap:TreasuryStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value3655377436173446338535673587344332103083285127052531250623662176202219911970146510519257976144215154673853214474934834115956405363275144485098061223
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.612.011.610.711.216.517.016.315.015.114.513.913.313.812.912.011.210.911.18.46.25.24.43.52.53.02.82.42.12.73.13.22.73.94.23.52.23.43.03.45.38.0

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value-5847-5055-4931-4527-4590-4647-4488-4265-3905-4043-4560-4541-4837-5093-4289-4301-4097-4220-4122-3923-4090-3847-2895-2607-2708-2621-3213-3435-3379-3307-3005-3115-3023-3188-2333-2078-2183-2300-2138-2246-2171-2098
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-18.6-16.1-15.9-14.1-15.2-21.5-21.2-20.2-18.3-19.8-23.2-23.4-25.5-28.0-23.4-23.8-22.6-23.2-23.3-22.5-24.3-21.6-16.1-14.8-16.3-15.4-18.9-21.7-21.7-20.3-19.1-20.5-20.1-20.6-15.4-13.4-14.5-15.0-14.3-15.0-14.2-13.8

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-63810701050517-2761109906777-364756794742-399895883810-581908874112-530971883638-380-593-503-376-251-450
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-13.725.126.511.9-6.829.925.920.8-9.120.523.821.2-11.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-245-167-74-5243-187-337-473-209-70-97-321-77-461-798-68-64-126-522-215-334-194-406-235-165-4168-116-168-142-62
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-5.3-3.9-1.9-120.6-4.6-9.1-13.5-5.6-1.8-2.6-9.6-2.2-13.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value1340-1031-987-15026826-563-515-526294-482-543-681697-284-407-621245-276-142-49471-1091121127-118-364-145-128-156260
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax28.8-24.2-24.9-34.5167.7-15.2-14.7-14.17.3-13.1-16.3-19.519.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-63810701050517-2761109906777-364756794742-399895883810-581908874112-530971883638-380-593-503-376-251-450
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-13.725.126.511.9-6.829.925.920.8-9.120.523.821.2-11.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value75439130333271615327653169029393501569436379472481375323419482294297431443303253388413241329347130282325168236248221176
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.29.27.67.617.64.17.914.217.20.811.814.316.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Profit Loss

us-gaap:ProfitLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value76739630634472715927953669630397507578441384480490381331429495299304438456259395424247337354135289331171242252225180
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.59.37.77.917.94.38.014.417.40.811.914.516.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value132826121163561469558968101357713711
Percentage of ProfitLoss1.77.18.53.51.53.81.10.90.93.31.01.21.61.11.31.71.81.62.42.32.61.72.31.62.91.82.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.70.70.30.30.20.10.10.10.00.10.20.30.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value75439130333271615327653169029393501569436379472481375323419482294297431443388413
Percentage of ProfitLoss98.398.799.096.598.596.298.999.199.196.799.098.898.498.998.798.398.298.497.697.797.498.397.798.497.198.297.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax16.29.27.67.617.64.17.914.217.20.811.814.316.20.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Depreciation Depletion And Amortization

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-245-167-74-5243-187-337-473-209-70-97-321-77-461-798-68-64-126-522-215-334-194-406-235-165-4168-116-168-142-62
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-5.3-3.9-1.9-120.6-4.6-9.1-13.5-5.6-1.8-2.6-9.6-2.2-13.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value1181371238873928777588573826279606351767385918383103998851678069
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value1340-1031-987-15026826-563-515-526294-482-543-681697-284-407-621245-276-142-49471-1091121127-118-364-145-128-156260
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax28.8-24.2-24.9-34.5167.7-15.2-14.7-14.17.3-13.1-16.3-19.519.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Proceeds From Issuance Of Long Term Debt

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value50330430345432534332572515333353332432223252252222
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Payments For Repurchase Of Common Stock

us-gaap:PaymentsForRepurchaseOfCommonStock



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312010-03-312009-03-31
Value18520010000175250250300200200200175215210200755504753002002502501001004020
Percentage of PaymentsForRepurchaseOfCommonStock100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value50330430345432534332572515333353332432223252252222
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Debt Instrument Interest Rate Stated Percentage

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-30
Value0.238-0.00500000000000000440.260.3740.230.00400000000000000360.2750.2560.2390.169999999999999980.2620.2860.233-0.0079999999999999520.2680.2950.2860.0070000000000000060.2790.2790.292-0.00400000000000000360.2960.2760.2950.3210.2890.2990.2680.2980.3020.3280.3110.2860.30.6740.2730.304
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber



Period End2019-12-312018-12-312018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value89101010111212131313141415161717192021222426283235384346
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value64.6953.9447.3939.1534.1430.9729.2929.129.2129.3332.14
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period

Share Based Compensation

us-gaap:ShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value72686760574747
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Liabilities

Deferred Tax Assets Net

Unrecognized Tax Benefits

us-gaap:UnrecognizedTaxBenefits



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value8286767474787272707164666665677076747710010097105105117128133120113117143176144143154152145199206293351
Percentage of UnrecognizedTaxBenefits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Valuation Allowance

us-gaap:DeferredTaxAssetsValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value54211839
Percentage of DeferredTaxAssetsValuationAllowance100.0100.0100.0100.0100.0

us-gaap:ValuationAllowanceByDeferredTaxAsset

mmc:DeferredTaxAssetsRelatedToNetOperatingLoss



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value7245111719827065
Percentage of DeferredTaxAssetsValuationAllowance133.3214.361.1566.7211.10.00.00.0

Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value188519211957201616250
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.00.0

Cash And Cash Equivalents Period Increase Decrease

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value1480115512131294111710669511036116812051026
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Proceeds From Repayments Of Short Term Debt

mmc:AcquisitionRelatedHedgingExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value00037-29341100000
Percentage of AcquisitionRelatedHedgingExpense0.00.00.0100.0100.0100.0100.00.00.00.0

mmc:AverageSharePriceCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value107.12.48000000000000499.9795.7488.540.079999999999998384.6881.6482.831.939999999999997779.3575.4171.321.179999999999999766.9864.1755.86-0.3699999999999974455.857.7556.371.25999999999999852.1549.6747.8442.0839.1536.2133.53
Percentage of AverageSharePriceCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:BusinessCombinationConsiderationTransferredAssetsAcquired



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value249362684131804214751693546276-15778391421056912983083021744904641260
Percentage of BusinessCombinationConsiderationTransferredAssetsAcquired100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

mmc:BusinessCombinationConsiderationTransferredNoncontrollingInterestsAssumed



Period End2019-12-312019-09-302018-12-312018-09-30
Value-15-1400
Percentage of BusinessCombinationConsiderationTransferredNoncontrollingInterestsAssumed100.0100.00.00.0

mmc:BusinessCombinationContingentandDeferredConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value440031352576257154090730262259831250727113140
Percentage of BusinessCombinationContingentandDeferredConsideration100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:BusinessAcquisition

mmc:CurrentFiscalPeriodAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value44031352576257154090730262259831250727113
Percentage of BusinessCombinationContingentandDeferredConsideration100.00.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:CommonStockDividendsPerShareCashDeclared



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value0.910.00.4550.4550.830.00.4150.4150.750.00.36999999999999990.380.680.00.34000000000000010.339999999999999970.620.00.309999999999999940.309999999999999940.560.00.280.280.50.249999999999999940.46
Percentage of CommonStockDividendsPerShareCashDeclared100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

mmc:DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value0.00.00.00.00.00.00.01000000.0
Percentage of DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations0.00.00.00.00.00.00.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-15-14-14-15-17-17-17-14
Percentage of DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations0.00.00.00.00.00.00.0-1400.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-30
Value0.00.00.00.01000000.00.00.01000000.00.01000000.01000000.01000000.0
Percentage of DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations0.00.00.00.00.00.00.0100.00.00.00.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-30
Value-41-45-46-45-38-41-39-32-31-30-29-33
Percentage of DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations0.00.00.00.00.00.00.0-3200.00.00.00.00.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-30
Value000010021222
Percentage of DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations0.00.00.00.00.00.00.0200.00.00.00.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-30
Value-56-59-60-60-55-58-56-46-45-44-13-17
Percentage of DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations0.00.00.00.00.00.00.0-4600.00.00.00.00.0

mmc:EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value-12-4559-106-2345-341-6520-87-17-1245112325174-41904521412-2336
Percentage of EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByLiabilityClass

mmc:FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments

mmc:ContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value-4-23-31-32-11-1210-20-4-20000
Percentage of FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.00.00.00.00.0

mmc:IncreaseDecreaseinOperatingLeaseLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-86-87-85-82-730000
Percentage of IncreaseDecreaseinOperatingLeaseLiabilities100.0100.0100.0100.0100.00.00.00.00.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

mmc:InterestIncomeFiduciaryAssets

us-gaap:OperatingSegments, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value121110111121111111111122
Percentage of InterestIncomeFiduciaryAssets100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value23253126231918151311119868665655666676810
Percentage of InterestIncomeFiduciaryAssets2300.01250.03100.02600.02300.00.01800.01500.01300.01100.0550.0900.0800.0600.0800.0600.0600.0500.0600.0500.0500.0600.0300.0300.00.00.00.00.00.0

us-gaap:StatementBusinessSegments

mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value2325312623191815135655666668
Percentage of InterestIncomeFiduciaryAssets2300.01250.03100.02600.02300.00.01800.01500.01300.0500.0600.0500.0500.0600.0300.0300.00.00.00.0

mmc:LeasesRightOfUseAssetAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value807985836800
Percentage of LeasesRightOfUseAssetAmortization100.0100.0100.0100.0100.00.00.0

mmc:OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-30
Value00204420005210100111000
Percentage of OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementBeforeTax0.00.0100.00.0100.0100.00.00.00.0100.0100.00.0100.00.00.0100.0100.0100.00.00.00.0

mmc:OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementNetofTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-30
Value00203340004310100111000
Percentage of OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementNetofTax0.00.0100.00.0100.0100.00.00.00.0100.0100.00.0100.00.00.0100.0100.0100.00.00.00.0

mmc:OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-30
Value000018000900000000000
Percentage of OtherComprehensiveIncomeLossFinalizationofPensionandOtherPostretirementBenefitPlanValuationEffectofSettlementTax0.00.00.00.0100.0100.00.00.00.0100.00.00.00.00.00.00.00.00.00.00.00.0

mmc:OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value135-806438-72120-15156-12076-215-47-151634011697101105-161169169119-91-17-106-23180-132
Percentage of OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentNetofTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value109-655629-59100-13129-10063-177-39-121343695818381-12813513394-71-15-81-18139-72
Percentage of OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentNetofTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value26-1589-1320-227-2013-38-8-329421161824-33343625-20-2-25-541-60
Percentage of OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:PaymentsForPreviousAcquisitionContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value4-1710681523012052811910141156
Percentage of PaymentsForPreviousAcquisitionContingentConsideration100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:PriorFiscalPeriodsAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-30
Value131310353514014253121353218861419246303
Percentage of PaymentsForPreviousAcquisitionContingentConsideration325.0185.7100.0583.3233.350.0133.3100.0210.0101.9150.0100.0184.2320.0128.6800.0600.0280.0316.70.00.00.00.00.0

mmc:PaymentsForPreviousAcquisitionDeferredConsideration



Period End2020-03-312019-12-312019-03-312018-12-312018-09-302018-06-302018-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value256233613401513621
Percentage of PaymentsForPreviousAcquisitionDeferredConsideration100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:PriorFiscalPeriodsAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value251402361340810112611414256222615136
Percentage of PaymentsForPreviousAcquisitionDeferredConsideration100.00.00.0100.0100.0100.0100.00.00.00.00.00.00.00.00.00.00.00.00.0100.0100.0100.0100.0

mmc:PaymentsforAcquisitionsDeferredandContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value295211029112115709306334233243972832274420
Percentage of PaymentsforAcquisitionsDeferredandContingentConsideration100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition, us-gaap:LongtermDebtType

mmc:PaymentsforDerivativeSettlement

mmc:JardineLloydThompsonGroupplc, us-gaap:SeniorNotes



Period End2019-12-312019-03-312019-03-31
Value077
Percentage of PaymentsforDerivativeSettlement0.0100.0

mmc:PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value85100979280417282961201231081066575726753291513411232593323020350
Percentage of PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

mmc:StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value14-39-44-4-35-2-71-27-38-13-3-660-1-14-48-5-11-16-53-3-13-7-60-11-25
Percentage of StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value1192492503918220311712368542617535255616954456117469675719486226
Percentage of StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency850.0-638.5-568.2-975.0-520.0-1000.0-442.91700.0-455.6-178.9-415.4-866.7-265.20.0-2500.0-400.0-352.1-1080.0-409.1-381.2-328.3-2300.0-515.4-814.3-323.3-781.8-904.0

us-gaap:StatementEquityComponents

us-gaap:AdjustmentsToAdditionalPaidInCapitalOther

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-03-31
Value-1000000.00.0
Percentage of AdjustmentsToAdditionalPaidInCapitalOther100.00.0

us-gaap:StatementEquityComponents

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-129242359-101464649-75373633-43302426-36152021-40112112-59-89-118-129
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllocatedShareBasedCompensationExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value7268676057474749503836472821232320181617161519152634414042
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AmortizationOfIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value8679841005148474345474240403132343330312424222220221817161716
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value1.490.610.911.420.30999999999999960.551.051.360.060000000000000050.770.981.110.83000000000000010.730.910.920.770.610.790.90.50.550.790.820.460.720.740.440.610.640.240.510.570.23-0.060.5
Percentage of BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value1.480.60.91.40.319999999999999840.541.041.340.060000000000000050.760.961.090.83000000000000010.730.90.920.750.610.780.890.49000000000000020.540.780.80.460.710.730.440.60.630.230.50.560.23-0.060.5
Percentage of BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value75442130646371715827553269030392502568430379472482400326422482297298431446253391417242330348131282321171239
Percentage of BusinessAcquisitionsProFormaNetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisitionsProFormaRevenue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value465742653967434640803824351437484002368433493496351536433137337633433526312032413215329531433306327729353099318728483030305828062930292925682655
Percentage of BusinessAcquisitionsProFormaRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationAcquisitionRelatedCosts

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value26484
Percentage of BusinessCombinationAcquisitionRelatedCosts100.0100.0100.0

us-gaap:BusinessCombinationConsiderationTransferred1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value24520574817737946915636432241509782142103598271299321993990444
Percentage of BusinessCombinationConsiderationTransferred1100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:CurrentFiscalPeriodAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value2450574817738246915636432241509782142103578271299321993990444
Percentage of BusinessCombinationConsiderationTransferred1100.00.0100.0100.0100.8100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.096.7100.0100.0100.0100.0100.0100.0100.0

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302018-09-202018-09-18
Value0052005200
Percentage of BusinessCombinationConsiderationTransferred10.00.00.00.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-30
Value20
Percentage of BusinessCombinationConsiderationTransferred1100.00.0

us-gaap:BusinessCombinationConsiderationTransferredLiabilitiesIncurred



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value5464027135487244555-27610700414839102195238240
Percentage of BusinessCombinationConsiderationTransferredLiabilitiesIncurred100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value-103609-186-127-56-177-204-29-91-4152-21483-691
Percentage of BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual

mmc:CurrentFiscalPeriodAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-09-302015-06-302014-09-302014-06-302013-09-30
Value4-691613-5-1-13-15101230550
Percentage of BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.00.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual

mmc:CurrentFiscalPeriodAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-09-302015-06-302014-09-302014-06-302013-09-30
Value153524864803611353403428874815463813
Percentage of BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value325-58-81-61826410115-85
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0

us-gaap:ChangeInUnrealizedGainLossOnForeignCurrencyFairValueHedgingInstruments1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value000-3729-341-1000000
Percentage of ChangeInUnrealizedGainLossOnForeignCurrencyFairValueHedgingInstruments10.00.00.0100.0100.0100.0100.00.00.00.00.0

us-gaap:CommonStockDividendsPerShareCashPaid



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value0.4550.4550.4150.4150.4150.4150.3750.3750.3750.3750.340.340.340.340.310.310.310.310.280.280.280.280.250.250.250.250.230.23
Percentage of CommonStockDividendsPerShareCashPaid100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiabilityRevenueRecognized



Period End2020-03-312019-03-31
Value289169
Percentage of ContractWithCustomerLiabilityRevenueRecognized100.0100.0

us-gaap:ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod



Period End2020-03-312019-03-31
Value2917
Percentage of ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod100.0100.0

us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents

us-gaap:CumulativeEffectOnRetainedEarningsNetOfTax1

us-gaap:AccountingStandardsUpdate201409, us-gaap:RetainedEarnings



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value00000003640000
Percentage of CumulativeEffectOnRetainedEarningsNetOfTax10.00.00.00.00.00.00.0100.00.00.00.00.0

us-gaap:AccountingStandardsUpdate201601, us-gaap:AccumulatedOtherComprehensiveIncome



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0000000-14
Percentage of CumulativeEffectOnRetainedEarningsNetOfTax10.00.00.00.00.00.00.0-3.8

us-gaap:DeferredIncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-09-302010-06-302010-03-312009-03-31
Value9-111391-9-10532231134410172525-52622-701243878202459513511026526510016
Percentage of DeferredIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0.00.01000000.00.00.01000000.00.00.00.00.00.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses0.00.0100.00.00.0100.00.00.00.00.00.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-18-11-11-11-11-14-14-14-13-9-9
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses0.00.0-1100.00.00.0-1400.00.00.00.00.00.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0.00.00.00.00.01000000.0-1000000.00.00.00.00.0-1000000.00.00.00.00.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses0.00.00.00.00.0100.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-22-16-14-15-15-22-22-23-24-33-33-33-31-22-24-24
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses0.00.0-1400.00.00.0-2200.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value001002-1000000100
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses0.00.0100.00.00.0200.00.00.00.00.00.00.00.00.00.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-40-27-25-26-26-36-36-37-37-42-42-43-40-41-43-42
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses0.00.0-2500.00.00.0-3600.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302017-12-312017-09-30
Value0.00.00.01000000.00.0-1000000.00.01000000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.00.0100.00.0100.00.0100.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-1000000.0-1000000.00.00.0-1000000.00.0-1000000.00.0-1000000.0-1000000.00.0-1000000.00.00.00.00.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.00.00.00.00.00.0-0.00.00.00.00.00.00.00.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0.00.00.00.00.0-1000000.00.0-1000000.00.0-1000000.00.0-1000000.00.0-1000000.01000000.0-1000000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.00.00.00.0-100.00.0100.00.00.00.00.00.00.00.00.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-1000000.0-1000000.00.00.0-1000000.01000000.0-1000000.0-1000000.0-1000000.0-1000000.01000000.00.01000000.01000000.01000000.01000000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.00.00.00.0100.00.0100.00.00.0100.00.00.00.00.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0.00.00.00.0-1000000.00.0-1000000.00.0-1000000.00.0-1000000.00.0-1000000.01000000.0-1000000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.00.00.0-100.00.0100.00.00.00.00.00.00.00.00.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.02720.00.00.00.03650.00.00.00.03210.00.00.00.03640.00.0
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate100.00.00.00.0100.00.00.00.0100.00.00.00.0100.00.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.02570.00.00.00.03480.00.00.00.03070.00.00.00.034-9.999999999999593e-050.0
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate94.50.00.00.095.30.00.00.095.60.00.00.093.40.00.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.05310.00.00.00.05740.00.00.00.05830.00.00.00.0664-0.000100000000000002860.0
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets100.00.00.00.0100.00.00.00.0100.00.00.00.0100.0100.00.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.01760.00.00.00.01740.00.00.00.01730.00.00.00.01770.00.0
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease100.00.00.00.0100.00.00.00.0100.00.00.00.0100.00.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value8686868586898990898989
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value124133128132127123124128132146143140135131137147
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets144.2154.7148.8155.3147.7138.2139.3142.2148.3164.0160.70.00.00.00.00.0

us-gaap:RetirementPlanType

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value210219214217213212213218221235232230224225232242
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets244.2254.7248.8255.3247.7238.2239.3242.2248.3264.0260.70.00.00.00.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0.00.01000000.00.00.00.00.01000000.00.01000000.00.0
Percentage of DefinedBenefitPlanInterestCost0.00.0100.00.00.00.00.0100.00.0100.00.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value5360616060595859596666
Percentage of DefinedBenefitPlanInterestCost0.00.06100.00.00.00.00.05900.00.06600.00.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value1000000.01000000.00.00.01000000.01000000.00.00.01000000.00.01000000.00.01000000.01000000.00.01000000.0
Percentage of DefinedBenefitPlanInterestCost0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value53675961595556585960595856646672
Percentage of DefinedBenefitPlanInterestCost0.00.05900.00.00.00.00.05800.00.06000.00.00.00.00.00.00.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value1110110111111201
Percentage of DefinedBenefitPlanInterestCost0.00.0100.00.00.00.00.0100.00.0100.00.00.00.00.00.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value106127120121119114114117118126125124122130132138
Percentage of DefinedBenefitPlanInterestCost0.00.012000.00.00.00.00.011700.00.012600.00.00.00.00.00.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0000001000101211
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost0.00.00.00.00.00.0100.00.00.00.0100.00.0100.0100.0100.0100.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-41-44-45-46-414-38-41-3918-31-31-30-28-29-37
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost0.00.00.00.00.00.0-3800.00.00.00.0-3100.00.0-3000.0-1400.0-2900.0-3700.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-03-31
Value0000001001212322-125
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost0.00.00.00.00.00.0100.00.00.00.0200.00.0200.0150.0200.0200.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-56-59-59-60-56-12-55-58-564-45-45-44-10-13-21
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost0.00.00.00.00.00.0-5500.00.00.00.0-4500.00.0-4400.0-500.0-1300.0-2100.0

us-gaap:DefinedBenefitPlanOtherCosts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-64-62-69-70-64-21-63-65-66-16-62-63-60
Percentage of DefinedBenefitPlanOtherCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0000000000212
Percentage of DefinedBenefitPlanOtherCosts-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-3.2-1.6-3.3

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-64-62-69-70-64-21-63-65-66-16-64-64-62
Percentage of DefinedBenefitPlanOtherCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0103.2101.6103.3

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0-300-4-42000-52-10-110-1
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements10.0100.00.00.0100.0100.00.00.00.0100.0100.00.0100.0100.00.0100.0

us-gaap:RetirementPlanType

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0-300-4-42000-52-10-110-1
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements10.0100.00.00.0100.0100.00.00.00.0100.0100.00.0100.0100.00.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanServiceCost

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0.00.00.00.00.00.01000000.00.00.01000000.00.00.00.01000000.01000000.00.0
Percentage of DefinedBenefitPlanServiceCost0.00.00.00.00.00.0100.00.00.0100.00.00.00.0100.0100.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value83101089871020191918181719
Percentage of DefinedBenefitPlanServiceCost0.00.00.00.00.00.0800.00.00.02000.00.00.00.01800.01700.00.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0.00.00.00.00.00.01000000.00.00.01000000.00.00.00.01000000.01000000.00.0
Percentage of DefinedBenefitPlanServiceCost0.00.00.00.00.00.0100.00.00.0100.00.00.00.0100.0100.00.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value83101089871020191918454346
Percentage of DefinedBenefitPlanServiceCost0.00.00.00.00.00.0800.00.00.02000.00.00.00.04500.04300.00.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedContributionPlanCostRecognized

country:GB



Period End2020-03-312019-03-312018-12-31
Value312219
Percentage of DefinedContributionPlanCostRecognized100.0100.0100.0

country:US



Period End2020-03-312019-12-312019-03-312018-12-31
Value37333533
Percentage of DefinedContributionPlanCostRecognized119.40.0159.1173.7

us-gaap:Depreciation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value978886857475777980787876807777767881777977777674756966678074
Percentage of Depreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:DividendsCommonStockCash

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value45964988123141902092103810193191350-117617832201621653011151153274138252
Percentage of DividendsCommonStockCash100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:DividendsShareBasedCompensationCash

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value486222221221121311111011103
Percentage of DividendsShareBasedCompensationCash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value-13270-704647-94-3
Percentage of EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent



Period End2020-03-312019-03-312018-03-31
Value-0.026-0.032-0.024
Percentage of EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent100.0100.0100.0

us-gaap:EquitySecuritiesFvNiRealizedGainLoss



Period End2020-03-312019-09-302019-03-312018-12-312018-09-30
Value-1431125
Percentage of EquitySecuritiesFvNiRealizedGainLoss100.0100.0100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value144691113865658-164-131353211110
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByLiabilityClass

mmc:ContingentConsideration



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value1691186558-16-1313532111101485411
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.00.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByLiabilityClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease

us-gaap:ForeignExchangeForward, mmc:ContingentConsideration



Period End2020-03-312019-09-302019-03-312018-09-30
Value00-42100
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease0.00.0100.0100.0

us-gaap:FairValueByLiabilityClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases

mmc:ContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value303-72911208206152034810831244184431255010
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0

us-gaap:FairValueByLiabilityClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements

mmc:ContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value13513103515351401425312135321886141924630313
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinitelivedIntangibleAssetsAcquired1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312017-09-302016-12-312016-09-302016-06-302016-03-31
Value91-77-4917347117315911972622142
Percentage of FinitelivedIntangibleAssetsAcquired1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-30
Value-68-49
Percentage of FinitelivedIntangibleAssetsAcquired188.3100.0

mmc:OtherAcquisitions



Period End2019-12-31
Value-9
Percentage of FinitelivedIntangibleAssetsAcquired111.7

us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass

mmc:JardineLloydThompsonGroupplc, us-gaap:CustomerRelationships



Period End2019-12-312019-09-30
Value-76-55
Percentage of FinitelivedIntangibleAssetsAcquired198.7112.2

mmc:JardineLloydThompsonGroupplc, us-gaap:OtherIntangibleAssets



Period End2019-12-312019-09-30
Value86
Percentage of FinitelivedIntangibleAssetsAcquired1-10.4-12.2

mmc:OtherAcquisitions, us-gaap:CustomerRelationships



Period End2019-12-31
Value-10
Percentage of FinitelivedIntangibleAssetsAcquired113.0

mmc:OtherAcquisitions, us-gaap:OtherIntangibleAssets



Period End2019-12-31
Value1000000.0
Percentage of FinitelivedIntangibleAssetsAcquired1-1.3

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CustomerRelationships



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302017-09-30
Value86-86-5516356714368
Percentage of FinitelivedIntangibleAssetsAcquired194.5111.7112.294.394.489.970.1

us-gaap:OtherIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312017-09-302016-12-312016-09-302016-06-302016-03-31
Value596994101602962202
Percentage of FinitelivedIntangibleAssetsAcquired15.5-11.7-12.25.75.65.810.10.029.923.7100.00.04.8

us-gaap:GainLossOnInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-2278512-5228012-250201-3-13702027-3132120198-16
Percentage of GainLossOnInvestments100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.00.0100.0100.0100.0100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:GainLossOnSaleOfOtherAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312010-03-312009-03-31
Value3-20-15-210-55201-10-3-6-30-1-216-20-142-2-1-1-2-12-26-12
Percentage of GainLossOnSaleOfOtherAssets100.0100.0100.0100.00.0100.0100.00.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:GainsLossesOnExtinguishmentOfDebt



Period End2019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302012-09-302011-09-30
Value00-320000-72
Percentage of GainsLossesOnExtinguishmentOfDebt0.00.0100.00.00.00.00.0100.0

us-gaap:GoodwillAcquiredDuringPeriod



Period End2020-03-312019-03-312018-03-312017-03-312016-03-312015-03-312014-03-312013-03-312012-03-312011-03-312010-03-31
Value1429715363611226708968157
Percentage of GoodwillAcquiredDuringPeriod100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0

us-gaap:GoodwillOtherIncreaseDecrease



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value401-32726058-43-18036118-90367-116-45-37-64-1860-22643
Percentage of GoodwillOtherIncreaseDecrease100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

us-gaap:IncomeLossFromEquityMethodInvestments



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-30
Value2352342720-14200-418-418-122
Percentage of IncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value46055-44535354555485532000
Percentage of IncomeLossFromEquityMethodInvestments0.0300.00.0100.0250.0-133.3100.0250.042.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-191042347-1327214612202-1460271
Percentage of IncomeLossFromEquityMethodInvestments0.0450.0333.380.0100.0100.0100.0350.0-14.30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.05.0

us-gaap:InvestmentType

us-gaap:PrivateEquityFunds



Period End2020-03-312019-03-31
Value-12
Percentage of IncomeLossFromEquityMethodInvestments0.0100.0

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value-140246-155-507926-33-10513576-41-860-5-6036-2153-128-46-5447-2653
Percentage of IncreaseDecreaseInAccountsPayableAndAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccruedIncomeTaxesPayable



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value91-78114-9096-27-31-4361-4032-1156-863061-2653-9968-37-16-233283917-20-3719
Percentage of IncreaseDecreaseInAccruedIncomeTaxesPayable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInEmployeeRelatedLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-1178435389216-886380302291-905341301309-888351296286-931342340268-927295352284-764-727-702-627-682-629
Percentage of IncreaseDecreaseInEmployeeRelatedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherCurrentAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value3443-34-3337-7-15-2-2-11-4-2543-11-1733440-46-28133-193554-15173
Percentage of IncreaseDecreaseInOtherCurrentAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets



Period End2020-03-312019-03-312015-06-302015-03-31
Value-571-158
Percentage of IncreaseDecreaseInOtherNoncurrentAssets100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-38-23-185-642-221-27173237455-46-94761-7139-4225-82-110-3646-85-37265015-113
Percentage of IncreaseDecreaseInOtherOperatingLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInReceivables



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value31346-353128309-132-17831357206-70172146-8-118105175-66-1562731-124-21024215012010117273-9
Percentage of IncreaseDecreaseInReceivables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestPaidNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value199402464398391182780
Percentage of InterestPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentIncomeInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value2542283233322210224333565554466695763436
Percentage of InvestmentIncomeInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LaborAndRelatedExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value255524782437253722822163208321352224209819061935194519181817187218541900187818261730189619041876183918241766180317601776179617531728172115861614165015331571
Percentage of LaborAndRelatedExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LeaseCost



Period End2020-03-312019-09-302019-06-302019-03-31
Value125131137116
Percentage of LeaseCost100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders

us-gaap:NoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-03-31
Value4291712718-15830122835615212170
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterestIncreaseFromBusinessCombination

us-gaap:NoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-3173951950000
Percentage of NoncontrollingInterestIncreaseFromBusinessCombination100.0100.0100.0100.00.00.00.00.0

us-gaap:StatementBusinessSegments

us-gaap:NumberOfBusinessesAcquired

mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value2.01.00.02.02.04.01.05.02.00.02.01.04.04.02.00.03.02.0
Percentage of NumberOfBusinessesAcquired100.0100.00.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.00.0100.0100.0

us-gaap:OperatingLeaseCost



Period End2020-03-312019-09-302019-06-302019-03-31
Value929410082
Percentage of OperatingLeaseCost100.0100.0100.0100.0

us-gaap:OperatingLeasePayments



Period End2020-03-312019-03-31
Value10387
Percentage of OperatingLeasePayments100.0100.0

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value00-10-1-1-1-1-1-10001101-2100-8-3-2-3-6-5-6-8
Percentage of OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax0.00.0100.00.0100.0100.0100.0100.0100.0100.00.00.00.0100.0100.00.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value0000-1-10-1-1-10001001-2100-6-2-1-2-4-3-4-2
Percentage of OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax0.00.00.00.0100.0100.00.0100.0100.0100.00.00.00.0100.00.00.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value00-1000-100000001000000-2-1-1-1-2-2-2-6
Percentage of OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax0.00.0100.00.00.00.0100.00.00.00.00.00.00.00.0100.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-03-312016-09-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-821-152-4194435-215-255-387123226-1793-119-244117-295-953-32568-121171-103-117
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value109-6695629-59-221-13129-100379-173-40-6-5083698806831-126128-64294-69-199-85-18139
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-13.3440.1-13.465.9-168.6102.85.1-33.3-81.30.00.00.0-2.70.0-211.80.086.0-57.1-12.7-107.7-43.467.4-28.9-101.5164.5-49.717.5-118.8

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value00000000-11-514-312100010000000-10
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-0.0-0.00.00.0-0.0-0.0-0.00.00.00.00.0-1.30.0-5.90.00.0-0.0-0.40.0-0.0-0.0-0.00.0-0.00.01.0-0.0

us-gaap:AccumulatedTranslationAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-930517-47515946-242-51622365126289235-404-54-33313-187-276243-423-311-41913778256-84-256
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax113.3-340.1113.434.1268.6-2.894.9133.3181.30.00.00.0104.00.0317.60.014.0157.1113.1207.7143.432.6128.9201.5-64.5149.781.6218.8

us-gaap:OtherComprehensiveIncomeLossBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-766-290-3937653-213-214-337144595-49309263-85131-171151-91-183163-190-1329-24994-128217-36-899-71175
Percentage of OtherComprehensiveIncomeLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-941514-47513969-237-52922865127290235-369-52-33413-181-278246-426-313-42113671254-85-260171-191162
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-11-30-2235-1350110352-106-23-3-2-2-1-7-2-1-44-140
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax100.0100.00.0100.0100.0100.0100.0100.0100.00.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:OtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-792-124-4046357-159-223-360152517-19296256-80412-204123-98-199167-243-952-288101-87222-56-72110-92165
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value138-6417148-37-16519156-71463-140-724-412651291108976-76180-641131-36-165-3429184
Percentage of OtherComprehensiveIncomeLossNetOfTax-17.4516.9-17.676.2-64.9103.8-8.5-43.3-46.789.6736.8-2.49.451.2541.7-63.289.4-90.8-38.2-45.5-74.167.3-45.5-35.6189.7-15.3-51.8-255.6

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value00000000-11-514-312100010000000-10
Percentage of OtherComprehensiveIncomeLossNetOfTax-0.0-0.00.00.0-0.0-0.0-0.00.0-2.126.34.7-1.2-1.58.3-0.00.0-0.0-0.50.0-0.0-0.0-0.00.0-0.00.01.8-0.0

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value-792-124-4046357-159-223-360152517-19296256-80412-204123-98-199167-243-952-288101-87-72165
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccumulatedTranslationAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-930517-47515946-242-51622365126289235-404-54-33313-187-276243-423-311-41913778256-84-256
Percentage of OtherComprehensiveIncomeLossNetOfTax117.4-416.9117.623.8164.9-3.8108.5143.3146.712.6-663.297.691.850.2-450.0163.210.6190.8138.7145.5174.132.7145.5135.6-89.7115.3150.0355.6

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-175804-82-6343222-23-19284-5481685-33502-82-163-138-90-9483-2361016-1724219937-50-25272-120-14
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-138641-71-4837165-19-15671-4631407-24412-65-129-110-89-7676-180641-1313616534-29-18458-86-5
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-37163-11-15657-4-3613-8528-2-990-17-34-28-1-187-56375-416343-21-6814-34-9
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value4034182529763536369443424042424342496876771254474875737260
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value-40-25-25-26-26-35-36-37-37-42-43-42-40-41-41-43-41-51-67-76-77-85-57-49-51-81-78-78-68
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value-29-21-19-20-20-26-29-28-30-41-33-33-30-31-29-31-29-29-44-50-52-59-39-34-36-55-50-49-16
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value-11-4-6-6-6-9-7-9-7-1-10-9-10-10-12-12-12-22-23-26-25-26-18-15-15-26-28-29-52
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value292815192259292729843333303229313027455052137333451474514
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value11636717697101091010131212222326251117141424262746
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-31
Value26-1661113-4-54923-878-30137-47193328716-453-37739-7-41-52064-1121103516-12
Percentage of OtherComprehensiveIncomeLossTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCostAndExpenseOperating



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-03-31
Value10261194106411328519288809088689018387967498137467787498447767707508147927777527047457167077327287437356916991042706626714
Percentage of OtherCostAndExpenseOperating100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForDerivativeInstrumentFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0002081290000
Percentage of PaymentsForDerivativeInstrumentFinancingActivities0.00.00.0100.0100.00.00.00.00.0

us-gaap:PaymentsForProceedsFromInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312010-03-312009-03-31
Value-57109-87-115-5-212-9-833-1-11-60222-27387-123119-20-925-19-6
Percentage of PaymentsForProceedsFromInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0

us-gaap:PaymentsForProceedsFromOtherInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-92544527-111-2-2-20-11-3-1-6-121510-1-11-1-5-2
Percentage of PaymentsForProceedsFromOtherInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForRestructuring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value384264141343933814181425107121041257914515292930
Percentage of PaymentsForRestructuring100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:JardineLloydThompsonGroupplc



Period End2020-03-312019-12-312019-09-30
Value6112283
Percentage of PaymentsForRestructuring160.53050.0319.2

us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve

mmc:JardineLloydThompsonGroupplc, mmc:InformationTechnology



Period End2020-03-312019-12-31
Value1736
Percentage of PaymentsForRestructuring44.7900.0

mmc:JardineLloydThompsonGroupplc, mmc:LegalConsultingandOtherOutsideServices



Period End2020-03-312019-12-312019-09-30
Value162437
Percentage of PaymentsForRestructuring42.1600.0142.3

mmc:JardineLloydThompsonGroupplc, mmc:RealEstateRelatedCosts



Period End2020-03-312019-12-312019-09-30
Value495
Percentage of PaymentsForRestructuring10.5225.019.2

mmc:JardineLloydThompsonGroupplc, us-gaap:EmployeeSeverance



Period End2020-03-312019-12-312019-09-30
Value245332
Percentage of PaymentsForRestructuring63.21325.0123.1

us-gaap:RestructuringCostAndReserve

us-gaap:EmployeeSeverance



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value31-422363725301847129216475212212231720
Percentage of PaymentsForRestructuring81.6-100.084.687.890.273.576.954.550.050.066.764.384.060.057.158.350.050.08.340.028.611.114.340.020.058.669.0

us-gaap:OtherRestructuring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value78454991547654435521135812312
Percentage of PaymentsForRestructuring18.4200.015.412.29.826.523.145.550.050.033.335.716.040.042.941.750.050.091.760.071.488.985.760.080.0

us-gaap:PaymentsOfDividendsCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value232235233212210213211194189195194176175178178165161164166151151153154138137127121117109102
Percentage of PaymentsOfDividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsOfFinancingCosts



Period End2019-12-312018-12-312017-12-31
Value0110
Percentage of PaymentsOfFinancingCosts0.0100.00.0

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value112021865016101048101371014781649365
Percentage of PaymentsRelatedToTaxWithholdingForShareBasedCompensation100.00.0100.0100.0100.0100.00.0100.0100.00.0100.00.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireAdditionalInterestInSubsidiaries



Period End2019-12-312019-09-302018-12-312018-09-30
Value52500
Percentage of PaymentsToAcquireAdditionalInterestInSubsidiaries100.0100.00.00.0

us-gaap:PaymentsToAcquireBusinessesGross



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value20105717142357393131292822014197751127755221221620149326333105390-9
Percentage of PaymentsToAcquireBusinessesGross100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:CurrentFiscalPeriodAcquisitions



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value201057171423573931312928220141977511277556212216201493263331
Percentage of PaymentsToAcquireBusinessesGross100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.7100.0100.0100.0100.0100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-30
Value20
Percentage of PaymentsToAcquireBusinessesGross0.00.0

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value20050536014034839212024262171411725112755211712441613833643191601041972
Percentage of PaymentsToAcquireBusinessesNetOfCashAcquired100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireEquityMethodInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0003880000
Percentage of PaymentsToAcquireEquityMethodInvestments0.00.00.0100.0100.00.00.00.00.0

us-gaap:PaymentsToMinorityShareholders



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312011-03-312010-03-312009-03-31
Value18-231141545681121915613214170121131524
Percentage of PaymentsToMinorityShareholders100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value7460165010511300000000301110
Percentage of ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates100.0100.0100.0100.00.0100.0100.0100.0100.00.00.00.00.00.00.00.00.0100.00.0100.0100.0

us-gaap:ProceedsFromIssuanceOfDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value000-36462-100592000987000347-85994945000798595050248
Percentage of ProceedsFromIssuanceOfDebt0.00.00.0100.0100.0100.00.00.0100.00.00.00.0100.00.00.00.0100.0100.0100.0100.0100.00.0100.0100.00.0100.0100.0

us-gaap:ProceedsFromIssuanceOrSaleOfEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value44262431772124163232402173342339924532431047354449213577891011
Percentage of ProceedsFromIssuanceOrSaleOfEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromLinesOfCredit



Period End2020-03-312019-03-31
Value20000
Percentage of ProceedsFromLinesOfCredit100.00.0

us-gaap:ProceedsFromRepaymentsOfCommercialPaper



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-06-302016-03-312015-06-302015-03-312014-06-302014-03-312013-03-31
Value193-224-199748-100-74249-1000100-252252500-1001000
Percentage of ProceedsFromRepaymentsOfCommercialPaper100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.00.0100.0100.00.0

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value0621102014031-14010101110111111
Percentage of ProceedsFromSaleOfPropertyPlantAndEquipment0.0100.0100.0100.0100.00.0100.00.0100.0100.00.0100.0100.0100.0100.00.0100.00.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-03-312016-09-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-29-28-15-19-22-56-32-27-29-30-29-30-21-45-50-52-1-37-33-34-51-47-45
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-29-28-15-19-22-56-32-27-29-84-33-33-30-96-29-31-30-21-45-50-52-1-37-33-34-51-47-45
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LongtermDebtType

us-gaap:RepaymentsOfDebt

us-gaap:SeniorNotes



Period End2020-03-312019-09-302018-10-312018-10-31
Value500300250250
Percentage of RepaymentsOfDebt100.0100.0100.0

us-gaap:RestructuringCharges



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value9561263866315868815935153203322442
Percentage of RestructuringCharges100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:JardineLloydThompsonGroupplc



Period End2020-03-312019-12-312019-09-30
Value8014358
Percentage of RestructuringCharges888.9255.4483.3

us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve

mmc:JardineLloydThompsonGroupplc, mmc:AcquisitionRelated



Period End2020-03-312019-09-302019-06-302019-03-31
Value80779820
Percentage of RestructuringCharges888.9641.71633.352.6

mmc:JardineLloydThompsonGroupplc, mmc:InformationTechnology



Period End2020-03-312019-12-31
Value2136
Percentage of RestructuringCharges233.364.3

mmc:JardineLloydThompsonGroupplc, mmc:LegalConsultingandOtherOutsideServices



Period End2020-03-312019-12-312019-09-30
Value20289
Percentage of RestructuringCharges222.250.075.0

mmc:JardineLloydThompsonGroupplc, mmc:RealEstateRelatedCosts



Period End2020-03-312019-12-312019-09-30
Value161721
Percentage of RestructuringCharges177.830.4175.0

mmc:JardineLloydThompsonGroupplc, us-gaap:EmployeeSeverance



Period End2020-03-312019-12-312019-09-30
Value236219
Percentage of RestructuringCharges255.6110.7158.3

us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve, us-gaap:StatementBusinessSegments

mmc:JardineLloydThompsonGroupplc, mmc:AcquisitionRelated, mmc:ConsultingSegment



Period End2020-03-312019-12-312019-09-302019-06-30
Value10855
Percentage of RestructuringCharges111.114.341.783.3

mmc:JardineLloydThompsonGroupplc, mmc:AcquisitionRelated, mmc:RiskandInsuranceServicesSegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value6195587519
Percentage of RestructuringCharges677.8169.6483.31250.050.0

us-gaap:ConsolidationItems, us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve

us-gaap:CorporateNonSegment, mmc:JardineLloydThompsonGroupplc, mmc:AcquisitionRelated



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value94014181
Percentage of RestructuringCharges100.071.4116.7300.02.6

us-gaap:ConsolidationItems, us-gaap:RestructuringCostAndReserve

us-gaap:CorporateNonSegment, mmc:SeveranceandFutureRentUnderNonCancelableLeasesandOtherCosts



Period End2020-03-312019-09-302019-06-302019-03-31
Value3223
Percentage of RestructuringCharges33.316.733.37.9

us-gaap:RestructuringCostAndReserve

us-gaap:EmployeeSeverance



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value529613759274657514535122141200220
Percentage of RestructuringCharges55.651.850.016.797.489.487.179.383.387.562.593.355.6100.0100.040.066.770.033.366.70.00.050.050.00.0

us-gaap:OtherRestructuring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value427651741211314003162122222
Percentage of RestructuringCharges44.448.250.083.32.610.612.920.716.712.537.56.744.40.00.060.033.330.066.733.3100.0100.050.050.0100.0

us-gaap:RestructuringCostAndReserve, us-gaap:Subsegments

mmc:SeveranceandConsultingCosts, mmc:MarshInsuranceGroup



Period End2020-03-31
Value2
Percentage of RestructuringCharges22.2

mmc:SeveranceandConsultingCosts, mmc:MercerConsultingGroup



Period End2020-03-312019-09-302019-06-302019-03-31
Value4102210
Percentage of RestructuringCharges44.483.3366.726.3

us-gaap:BusinessAcquisition

us-gaap:RestructuringReserveSettledWithoutCash2

mmc:JardineLloydThompsonGroupplc



Period End2020-03-312019-12-31
Value1316
Percentage of RestructuringReserveSettledWithoutCash2100.0100.0

us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve

mmc:JardineLloydThompsonGroupplc, mmc:LegalConsultingandOtherOutsideServices



Period End2020-03-312019-12-31
Value14
Percentage of RestructuringReserveSettledWithoutCash27.725.0

us-gaap:RestructuringReserveTranslationAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-03-312014-12-312014-09-30
Value-50-8-42-34-1025-1-3-30-1-13-11-1
Percentage of RestructuringReserveTranslationAdjustment100.00.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:RestructuringCostAndReserve

us-gaap:EmployeeSeverance



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-31
Value-10-3-10-430-112-1-1-1000-11
Percentage of RestructuringReserveTranslationAdjustment20.00.037.525.00.0133.375.0-0.00.050.040.0100.033.333.30.0-0.0-0.0-33.3100.0

us-gaap:OtherRestructuring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-03-312014-12-312014-09-30
Value-40-5-3211-11130-2-20-1-14-100
Percentage of RestructuringReserveTranslationAdjustment80.00.062.575.0100.0-33.325.0100.00.050.060.0-0.066.766.70.0100.0100.0133.3100.00.0-0.0

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability



Period End2020-03-312019-03-31
Value790
Percentage of RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability100.00.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value200030002100300
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShortTermLeaseCost



Period End2020-03-312019-09-302019-06-302019-03-31
Value1421
Percentage of ShortTermLeaseCost100.0100.0100.0100.0

us-gaap:StockIssued1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value2011241581131250128521367413643310928130
Percentage of StockIssued1100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:SubleaseIncome



Period End2020-03-312019-09-302019-06-302019-03-31
Value5444
Percentage of SubleaseIncome100.0100.0100.0100.0

us-gaap:StatementClassOfStock

us-gaap:TreasuryStockSharesAcquired

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value012100233322223331985345232
Percentage of TreasuryStockSharesAcquired0.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:TreasuryStockValueAcquiredCostMethod

us-gaap:TreasuryStock



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value2853001000017525025030020020020017521521020075550475300200250250100100
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:VariableLeaseCost



Period End2020-03-312019-09-302019-06-302019-03-31
Value37373937
Percentage of VariableLeaseCost100.0100.0100.0100.0

us-gaap:WeightedAverageNumberDilutedSharesOutstandingAdjustment



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value55566567675455667789898
Percentage of WeightedAverageNumberDilutedSharesOutstandingAdjustment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:AccruedFeesandOtherRevenueReceivableGrossCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value5028460846365057431539844077428842173777365137403564337033163473335731983255340431353142326634613209306531202858
Percentage of AccruedFeesandOtherRevenueReceivableGrossCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansAdjustmentTax



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value-16351493146215301519158712131657
Percentage of AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansAdjustmentTax100.0100.0100.0100.0100.0100.0100.0100.0

mmc:AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value1415-11-9-8-579
Percentage of AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax100.0100.0100.0100.0100.0100.0100.0100.0

mmc:AdvancedPremiumsandClaimsReceivableGrossCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value11312312691597956627065524953835347605160545650775955616262
Percentage of AdvancedPremiumsandClaimsReceivableGrossCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

mmc:BusinessCombinationContingentConsiderationAssetFairValueDisclosure

us-gaap:OtherAssets, us-gaap:FairValueInputsLevel3, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value828465650
Percentage of BusinessCombinationContingentConsiderationAssetFairValueDisclosure100.0100.0100.0100.00.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherAssets, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value828465650
Percentage of BusinessCombinationContingentConsiderationAssetFairValueDisclosure100.0100.0100.0100.00.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

mmc:BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure

mmc:AccountsPayableandAccruedLiabilitiesandOtherLiabilities, us-gaap:FairValueInputsLevel3, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value2392251851961711831681851611891702032472412322793023092832442062071511441331049263
Percentage of BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

mmc:AccountsPayableandAccruedLiabilitiesandOtherLiabilities, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value2392251851961711831681851611891702032472412322793023092832442062071511441331049263
Percentage of BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetsIncludingGoodwill

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value864386138587
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetsIncludingGoodwill100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value368365365
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetsIncludingGoodwill4.34.24.3

mmc:TotalAcquisitions



Period End2019-12-31
Value9011
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetsIncludingGoodwill104.3

us-gaap:BusinessAcquisition

mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCashandInvestmentsHeldinFiduciaryCapacityNoncurrent

mmc:TotalAcquisitions



Period End2019-12-31
Value1275
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCashandInvestmentsHeldinFiduciaryCapacityNoncurrent100.0

us-gaap:BusinessAcquisition

mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedFiduciaryLiabilitiesGrossNoncurrent

mmc:TotalAcquisitions



Period End2019-12-31
Value1275
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedFiduciaryLiabilitiesGrossNoncurrent100.0

dei:LegalEntity

mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityDefinedBenefitPlanNoncurrent

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-06-302019-03-31
Value1003234248
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityDefinedBenefitPlanNoncurrent100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value248248234
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityDefinedBenefitPlanNoncurrent24.70.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value248
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityDefinedBenefitPlanNoncurrent24.7

us-gaap:BusinessAcquisition

mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityForErrorsAndOmissions

mmc:TotalAcquisitions



Period End2019-12-31
Value31
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLiabilityForErrorsAndOmissions100.0

us-gaap:BusinessAcquisition

mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value389389386
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value389
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent100.0

us-gaap:BusinessAcquisition

mmc:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseRightofUseAsset

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value382382379
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseRightofUseAsset100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value382
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseRightofUseAsset100.0

mmc:CashCashEquivalentsRestrictedCashandRestrictedCashEquivalentsandFundsHeldinAcquisitionRelatedEscrow



Period End2020-03-312019-03-312018-03-31
Value148074761168
Percentage of CashCashEquivalentsRestrictedCashandRestrictedCashEquivalentsandFundsHeldinAcquisitionRelatedEscrow100.0100.0100.0

mmc:CashandInvestmentsHeldinFiduciaryCapacityNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value7661734475476807524350015185511851404847512850394601424145324538450141464374486945854552487152374814423446573992
Percentage of CashandInvestmentsHeldinFiduciaryCapacityNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:DeferredTaxAssetsDeferredIncomeNetOfValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value1920497170757475
Percentage of DeferredTaxAssetsDeferredIncomeNetOfValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0

mmc:DeferredTaxAssetsNetNetOfValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value13701186104915151545165414071939
Percentage of DeferredTaxAssetsNetNetOfValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0

mmc:DeferredTaxAssetsOperatingLossCarryforwardsDomesticNetOfValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value70486756705779104
Percentage of DeferredTaxAssetsOperatingLossCarryforwardsDomesticNetOfValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0

mmc:DeferredTaxAssetsOperatingLossCarryforwardsForeignNetofValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value324170139127120119140159
Percentage of DeferredTaxAssetsOperatingLossCarryforwardsForeignNetofValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0

mmc:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensionsAndPostretirementBenefitsNetofValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value438406394629630
Percentage of DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensionsAndPostretirementBenefitsNetofValuationAllowance100.0100.0100.0100.0100.0

mmc:DeferredTaxAssetsTaxDeferredExpenseOtherNetOfValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value2716315049849077
Percentage of DeferredTaxAssetsTaxDeferredExpenseOtherNetOfValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0

mmc:DeferredTaxAssetsTaxDeferredExpenseReservesandAccrualsNetofValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value492526369582586572570589
Percentage of DeferredTaxAssetsTaxDeferredExpenseReservesandAccrualsNetofValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

mmc:DefinedBenefitPlanCumulativeEmployerContributionsInExcessOfNetPeriodicCost

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-33-37-40
Percentage of DefinedBenefitPlanCumulativeEmployerContributionsInExcessOfNetPeriodicCost100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value507429332
Percentage of DefinedBenefitPlanCumulativeEmployerContributionsInExcessOfNetPeriodicCost-1536.4-1159.5-830.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value-67-68-73-70
Percentage of DefinedBenefitPlanCumulativeEmployerContributionsInExcessOfNetPeriodicCost203.0183.8182.50.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value4049390739383385
Percentage of DefinedBenefitPlanCumulativeEmployerContributionsInExcessOfNetPeriodicCost-12269.7-10559.5-9845.00.0

mmc:DefinedContributionPlanEmployeeStockOwnershipPlanESOPSharesinESOPValue



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value556444499436398453453375
Percentage of DefinedContributionPlanEmployeeStockOwnershipPlanESOPSharesinESOPValue100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

mmc:EquityMethodInvestmentOwnershipPercentageSold

mmc:AlexanderForbesGroupHoldingsLimited



Period End2020-02-29
Value0.04
Percentage of EquityMethodInvestmentOwnershipPercentageSold100.0

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:StatementScenario

mmc:AlexanderForbesGroupHoldingsLimited, srt:ScenarioForecast



Period End2020-06-30
Value0.15
Percentage of EquityMethodInvestmentOwnershipPercentageSold0.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

mmc:FiduciaryAssetsFairValueDisclosure

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value13440043334760100691293611150822890692792487966955777141404149
Percentage of FiduciaryAssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

us-gaap:FairValueInputsLevel2, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value000000000000000000000000003
Percentage of FiduciaryAssetsFairValueDisclosure0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.02.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring, us-gaap:MoneyMarketFunds



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value134360433347608069129111
Percentage of FiduciaryAssetsFairValueDisclosure100.090.0100.0100.0100.080.0100.0100.0100.0

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring, us-gaap:USTreasurySecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value040000200
Percentage of FiduciaryAssetsFairValueDisclosure0.010.00.00.00.020.00.0

us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value13440043334760100691293611150822890692792487966955777141404152
Percentage of FiduciaryAssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0102.0

us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument

us-gaap:FairValueMeasurementsRecurring, us-gaap:MoneyMarketFunds



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value134360433347608069129111
Percentage of FiduciaryAssetsFairValueDisclosure100.090.0100.0100.0100.080.0100.0100.0100.0

us-gaap:FairValueMeasurementsRecurring, us-gaap:USTreasurySecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value040000200
Percentage of FiduciaryAssetsFairValueDisclosure0.010.00.00.00.020.00.0

mmc:FiduciaryLiabilitiesGrossNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value7661734475476807524350015185511851404847512850394601424145324538450141464374486945854552487152374814423446573992
Percentage of FiduciaryLiabilitiesGrossNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:LiabilityForErrorsAndOmissions



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value343335324319282287303303312301316305300308317322319318358357334341355366354373380440433460476466472468446451452430441517518512
Percentage of LiabilityForErrorsAndOmissions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:PaymentofContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312016-03-312015-12-312015-09-302015-03-31
Value966029720-1100221401622447612
Percentage of PaymentofContingentConsideration100.0100.0100.00.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

mmc:PaymentsForPreviousAcquisitionDeferredandContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312016-03-312015-12-312015-09-302015-03-31
Value2952110291121157093063342332439397332
Percentage of PaymentsForPreviousAcquisitionDeferredandContingentConsideration100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:StockholdersEquitySubtotalBeforeTreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value1110611717114141178311371111511112511240112311052599829779915087789120888187938593831383377914805887128842846484907587723170347053707368276676653571057316701469296863652366696983
Percentage of StockholdersEquitySubtotalBeforeTreasuryStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mmc:UncollectedPremiumsandClaimsNetofRelatedPayables



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value97008900960011000920073007800830076006800680077007800700070007800760069007400890081007300780087008700820090009100
Percentage of UncollectedPremiumsandClaimsNetofRelatedPayables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsReceivableGrossCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value570253765337569547464429460047174676424340144087389537393687380737353558361037553476347236013812356434083401344532812858316832093114267626822895270425442506253824292418
Percentage of AccountsReceivableGrossCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType, us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncomeLossBeforeTax1

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLoss



Period End2019-12-312018-12-312017-12-312016-12-31
Value46611
Percentage of AccumulatedOtherComprehensiveIncomeLossBeforeTax1100.0100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit, us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLoss



Period End2019-12-312018-12-312017-12-312016-12-31
Value-2114-1896-1766-1720
Percentage of AccumulatedOtherComprehensiveIncomeLossBeforeTax1-52850.0-31600.0-29433.3-15636.4

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCredit



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value11121500
Percentage of AccumulatedOtherComprehensiveIncomeLossBeforeTax1275.0200.0250.00.00.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLoss



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value-5-1-10-11-6
Percentage of AccumulatedOtherComprehensiveIncomeLossBeforeTax1-125.0-16.7-166.7-100.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit, us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCredit



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value-2-24343-3
Percentage of AccumulatedOtherComprehensiveIncomeLossBeforeTax1-50.0-33.3716.7390.90.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit, us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLoss



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value-3055-2568-2646-3081-2887
Percentage of AccumulatedOtherComprehensiveIncomeLossBeforeTax1-76375.0-42800.0-44100.0-28009.10.0

us-gaap:AdditionalPaidInCapitalCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value7468627967366818177717326827847837637338428127897778618518428379309229149091028101010029931107107610531018115611231092105011851159110912111245
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-312007-12-31
Value14414013914211611212411611411010510310096848688879396969510510610298107100105106109107106105112123121114111113117103109
Percentage of AllowanceForDoubtfulAccountsReceivableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:AssetsFairValueDisclosure

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value549225199228233402303276246382296283241252212176146282446182176257498222210199169622
Percentage of AssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueInputsLevel2, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value8888888000000000000000022336
Percentage of AssetsFairValueDisclosure1.53.64.03.53.42.02.60.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.91.01.51.81.0

us-gaap:FairValueInputsLevel3, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value82846565000000000000000000000000
Percentage of AssetsFairValueDisclosure14.937.332.728.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value639317272301241410311276246382296283241252212176146282446182176257498224212202172628
Percentage of AssetsFairValueDisclosure116.4140.9136.7132.0103.4102.0102.6100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.9101.0101.5101.8101.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value280295309
Percentage of BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value280
Percentage of BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value349353353
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value766
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents2.01.71.7

mmc:TotalAcquisitions



Period End2019-12-31
Value356
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents102.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value132143143
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value132
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value695714714
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value656
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables0.90.70.8

mmc:TotalAcquisitions



Period End2019-12-31
Value701
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables100.9

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value708689699
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value955
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities1.30.70.7

mmc:TotalAcquisitions



Period End2019-12-31
Value717
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities101.3

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value666557
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value66
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value154516131662
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value134143143
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill8.78.98.6

mmc:TotalAcquisitions



Period End2019-12-31
Value1679
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill108.7

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value279527502710
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value988
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities0.30.30.3

mmc:TotalAcquisitions



Period End2019-12-31
Value2804
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities100.3

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-302019-04-01
Value1044104410441000
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt100.0100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value1044
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value375349316
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value033
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther0.00.90.9

mmc:TotalAcquisitions



Period End2019-12-31
Value375
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value473493503
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value481
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets101.7

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment

mmc:JardineLloydThompsonGroupplc



Period End2019-12-312019-09-302019-06-30
Value898981
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment100.0100.0100.0

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value122
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment1.12.22.5

mmc:TotalAcquisitions



Period End2019-12-31
Value90
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment101.1

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest

mmc:OtherAcquisitions



Period End2019-12-312019-09-302019-06-30
Value359357357
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest100.0100.0100.0

mmc:TotalAcquisitions



Period End2019-12-31
Value5927
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest1651.0

us-gaap:CapitalizedComputerSoftwareAccumulatedAmortization



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value1400130013001100958837748691619572505
Percentage of CapitalizedComputerSoftwareAccumulatedAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CapitalizedComputerSoftwareNet



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value496435488482498501399278244215214
Percentage of CapitalizedComputerSoftwareNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CapitalizedContractCost

us-gaap:CapitalizedContractCostNet

mmc:CoststoFulfill



Period End2019-12-312018-12-312018-09-302018-06-302018-03-31
Value262227160154171
Percentage of CapitalizedContractCostNet100.0100.0100.0100.0100.0

mmc:CoststoObtain



Period End2019-12-312018-12-312018-09-302018-06-302018-03-31
Value222206203196194
Percentage of CapitalizedContractCostNet84.790.7126.9127.3113.5

mmc:DeferredImplementationCosts



Period End2019-12-312018-12-312018-09-302018-06-302018-03-31
Value3041413939
Percentage of CapitalizedContractCostNet11.518.125.625.322.8

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:CashAndCashEquivalentsFairValueDisclosure

us-gaap:CashAndCashEquivalents, us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value4085537716711831332714354362422724314140310403610734872664523483
Percentage of CashAndCashEquivalentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

us-gaap:CashAndCashEquivalents, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value4085537716711831332714354362422724314140310403610734872664523483
Percentage of CashAndCashEquivalentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value193032554974807517524900150150500
Percentage of CommercialPaper100.00.0100.0100.0100.00.0100.0100.0100.00.00.0100.0100.0100.00.0

us-gaap:ContractWithCustomerAssetNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312019-01-012018-12-312018-09-302018-06-302018-03-312018-01-012017-12-31
Value270207240275198112112139178169128128
Percentage of ContractWithCustomerAssetNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiability



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312019-01-012018-12-312018-09-302018-06-302018-03-312018-01-012017-12-31
Value659593611641611545545577647657583583
Percentage of ContractWithCustomerLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtInstrument, us-gaap:LongtermDebtType

us-gaap:DebtInstrumentFaceAmount

mmc:SeniorDebtObligations4.375Due2029, us-gaap:SeniorNotes



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312019-01-31
Value150015001500150015001250
Percentage of DebtInstrumentFaceAmount100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:DebtInstrument, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:DebtInstrumentFairValue

us-gaap:LongTermDebt, mmc:SeniorDebtObligationsDue2014, us-gaap:FairValueInputsLevel2, us-gaap:FairValueMeasurementsRecurring



Period End2019-12-312018-12-312017-12-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value0116000252252253253256
Percentage of DebtInstrumentFairValue0.0100.00.00.00.0100.0100.0100.0100.0100.0

us-gaap:LongTermDebt, mmc:SeniorDebtObligationsDue2014, us-gaap:FairValueInputsLevel3, us-gaap:FairValueMeasurementsRecurring



Period End2019-12-312018-12-312017-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value03250000000
Percentage of DebtInstrumentFairValue0.0280.20.00.00.00.00.00.00.0

us-gaap:BalanceSheetLocation, us-gaap:DebtInstrument, us-gaap:FairValueByMeasurementFrequency

us-gaap:LongTermDebt, mmc:SeniorDebtObligationsDue2014, us-gaap:FairValueMeasurementsRecurring



Period End2019-12-312018-12-312017-12-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value0441000252252253253256
Percentage of DebtInstrumentFairValue0.0380.20.00.00.0100.0100.0100.0100.0100.0

us-gaap:DebtInstrument

us-gaap:DebtInstrumentUnusedBorrowingCapacityAmount

mmc:OtherDebtFacilities



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value598594624376229260282247
Percentage of DebtInstrumentUnusedBorrowingCapacityAmount100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Range

us-gaap:DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible

srt:Maximum



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value1310710101098
Percentage of DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredIncomeTaxAssetsNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-31
Value69467660362868068049753255455266994797510091097108510931138
Percentage of DeferredIncomeTaxAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation

us-gaap:OtherNoncurrentAssets



Period End2019-12-312018-12-31
Value676680
Percentage of DeferredIncomeTaxAssetsNet100.0100.0

us-gaap:DeferredIncomeTaxLiabilities



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value1259927761618644484479358
Percentage of DeferredIncomeTaxLiabilities100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation

us-gaap:DeferredIncomeTaxLiabilitiesNet

us-gaap:OtherNoncurrentLiabilities



Period End2019-12-312018-12-31
Value565421
Percentage of DeferredIncomeTaxLiabilitiesNet100.0100.0

us-gaap:IncomeTaxAuthority

us-gaap:DeferredTaxAssetsOperatingLossCarryforwards

us-gaap:DomesticCountry



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value32367103
Percentage of DeferredTaxAssetsOperatingLossCarryforwards100.0100.0100.0100.0100.0100.0

us-gaap:ForeignCountry



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value845731313696
Percentage of DeferredTaxAssetsOperatingLossCarryforwards262.51900.0516.7442.9360.03200.0

us-gaap:StateAndLocalJurisdiction



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value344249485540
Percentage of DeferredTaxAssetsOperatingLossCarryforwards106.21400.0816.7685.7550.01333.3

us-gaap:DeferredTaxLiabilitiesDeferredExpense



Period End2019-12-312018-12-312017-12-31
Value77780
Percentage of DeferredTaxLiabilitiesDeferredExpense100.0100.00.0

us-gaap:DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value151171172109441890
Percentage of DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:DeferredTaxLiabilitiesOther



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value37491614653491520
Percentage of DeferredTaxLiabilitiesOther100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxLiabilitiesPropertyPlantAndEquipment



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value594342338377368307273245
Percentage of DeferredTaxLiabilitiesPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxLiabilitiesUndistributedForeignEarnings



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value40028723521717613111210799174174
Percentage of DeferredTaxLiabilitiesUndistributedForeignEarnings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAccumulatedBenefitObligation

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value632255296221
Percentage of DefinedBenefitPlanAccumulatedBenefitObligation100.0100.0100.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value11079875297839397
Percentage of DefinedBenefitPlanAccumulatedBenefitObligation175.2158.3157.30.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value466
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-2114-1896-1766
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax-52850.0-31600.0-29433.3

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value6115-11
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax150.0183.383.30.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value-3057-2570-2603-3038
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax-76425.0-42833.3-43383.30.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-4-6-6
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value211418961766
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax-52850.0-31600.0-29433.3

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value511011
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax-125.0-16.7-166.70.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value3055256826463081
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax-76375.0-42800.0-44100.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value1112150
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax100.0100.0100.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value-2-24343
Percentage of DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax-18.2-16.7286.70.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmountsRecognizedInBalanceSheet

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-29-31-34
Percentage of DefinedBenefitPlanAmountsRecognizedInBalanceSheet100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-1607-1467-1434
Percentage of DefinedBenefitPlanAmountsRecognizedInBalanceSheet5541.44732.34217.6

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value-61-57-68-81
Percentage of DefinedBenefitPlanAmountsRecognizedInBalanceSheet210.3183.9200.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value99213371335347
Percentage of DefinedBenefitPlanAmountsRecognizedInBalanceSheet-3420.7-4312.9-3926.50.0

us-gaap:DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value1619163218571821181516881814180818571693115598187277612531197118111591182114810109671007980889979780668580260225140673947742134426527114094150
Percentage of DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value163216871684766
Percentage of DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent100.099.999.598.7

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value0.0310.04240.0367
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value0.03440.04450.0386
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate111.0105.0105.2

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value0.02530.03320.02970.0342
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate81.678.380.90.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value0.02090.02890.02580.0269
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate67.468.270.30.0

us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value0.02720.03650.03210.0364
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate87.786.187.50.0

us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value0.02570.03480.03070.034
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate82.982.183.70.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value0.02750.02820.0280.0285
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease100.0100.0100.0100.0

us-gaap:RetirementPlanType

us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value0.01760.01740.01730.0177
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease64.061.761.862.1

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanBenefitObligation

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value31323637
Percentage of DefinedBenefitPlanBenefitObligation100.0100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value6322552962215894
Percentage of DefinedBenefitPlanBenefitObligation20393.517278.117280.615929.7

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value6157688179
Percentage of DefinedBenefitPlanBenefitObligation196.8178.1188.9218.90.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-312015-12-31
Value1132189691005396709076
Percentage of DefinedBenefitPlanBenefitObligation36519.428028.127925.026135.10.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedAmortizationNextFiscalYear

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value905988
Percentage of DefinedBenefitPlanExpectedAmortizationNextFiscalYear100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value-72-44
Percentage of DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear100.0100.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-90-59-90
Percentage of DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear125.0134.10.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value00-2
Percentage of DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear0.00.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-31
Value1112
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value16751626
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter15227.313550.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value151517
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter136.4125.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value201917681837
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter18354.514733.30.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value281264
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths100.0100.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value322272279
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths114.6103.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value318306
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive100.0100.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value368320326
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive115.7104.60.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value312299
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour100.0100.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value358302316
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour114.7101.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-31
Value34
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value305291
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree10166.77275.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value334
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree100.075.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value338291305
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree11266.77275.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value293277
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo100.0100.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value334
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo1.01.10.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value328282297
Percentage of DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo111.9101.80.0

us-gaap:RetirementPlanName, us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear

mmc:JardineLloydThompsonUnitedKingdomPlan, country:GB, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-31
Value28
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear100.0

us-gaap:RetirementPlanSponsorLocation

country:US



Period End2019-12-31
Value76
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear271.4

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value846582
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear300.00.00.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanFundedStatusOfPlan

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-29-31-34
Percentage of DefinedBenefitPlanFundedStatusOfPlan100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value-1607-1467-1434
Percentage of DefinedBenefitPlanFundedStatusOfPlan5541.44732.34217.6

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value-61-57-68-81
Percentage of DefinedBenefitPlanFundedStatusOfPlan210.3183.9200.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value99213371335347
Percentage of DefinedBenefitPlanFundedStatusOfPlan-3420.7-4312.9-3926.50.0

us-gaap:DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear



Period End2019-12-312018-12-312017-12-31
Value0.04980.05090.0512
Percentage of DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

country:US, mmc:PensionandPostretirementBenefitPlan



Period End2019-12-312018-12-31
Value0.060.0619
Percentage of DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear120.5121.6

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets

us-gaap:ForeignPlan



Period End2019-12-312018-12-31
Value23001600
Percentage of DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-31
Value47004100
Percentage of DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets204.3256.2

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation

us-gaap:ForeignPlan



Period End2019-12-312018-12-31
Value30001900
Percentage of DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value630055006200
Percentage of DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation210.0289.50.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation

us-gaap:ForeignPlan



Period End2019-12-312018-12-31
Value27001600
Percentage of DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value630055006200
Percentage of DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation233.3343.80.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets

us-gaap:ForeignPlan



Period End2019-12-312018-12-31
Value22001300
Percentage of DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value470041004800
Percentage of DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets213.6315.40.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation

us-gaap:ForeignPlan



Period End2019-12-312018-12-31
Value29001700
Percentage of DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value630055006200
Percentage of DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateProjectedBenefitObligation217.2323.50.0

us-gaap:DefinedBenefitPlanUltimateHealthCareCostTrendRate1



Period End2019-12-312018-12-312017-12-31
Value0.04340.04460.0441
Percentage of DefinedBenefitPlanUltimateHealthCareCostTrendRate1100.0100.0100.0

us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanWeightedAverageAssetAllocations

us-gaap:EquityFunds, country:GB



Period End2020-03-312019-12-312019-09-30
Value0.30.350.33
Percentage of DefinedBenefitPlanWeightedAverageAssetAllocations100.0100.0100.0

us-gaap:EquityFunds, country:US



Period End2020-03-312019-12-312019-09-302018-12-31
Value0.60.640.620.62
Percentage of DefinedBenefitPlanWeightedAverageAssetAllocations200.0182.9187.90.0

us-gaap:FixedIncomeFunds, country:GB



Period End2020-03-312019-12-312019-09-30
Value0.70.650.67
Percentage of DefinedBenefitPlanWeightedAverageAssetAllocations233.3185.7203.0

us-gaap:FixedIncomeFunds, country:US



Period End2020-03-312019-12-312019-09-302018-12-31
Value0.40.360.380.38
Percentage of DefinedBenefitPlanWeightedAverageAssetAllocations133.3102.9115.20.0

us-gaap:DerivativeLiabilities



Period End2019-12-312018-12-312017-12-31
Value04410
Percentage of DerivativeLiabilities0.0100.00.0

us-gaap:EmployeeRelatedLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value101821971762137589217781406110381317181377107376516551310101572416561313974706163313389857011466119485874614731225916699140011068716671294104363713191224
Percentage of EmployeeRelatedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:EquityMethodInvestmentOwnershipPercentage

mmc:AlexanderForbesGroupHoldingsLimited



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312016-09-302016-06-302014-12-31
Value0.310.340.330.330.330.330.330.34
Percentage of EquityMethodInvestmentOwnershipPercentage100.0100.0100.0100.0100.0100.0100.0100.0

mmc:MarshIndiaInsuranceBrokersLimited



Period End2019-12-312019-01-012018-12-312016-09-302016-06-30
Value0.260.490.260.260.26
Percentage of EquityMethodInvestmentOwnershipPercentage76.50.00.078.878.8

us-gaap:EquityMethodInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312013-12-31
Value37143445243938828729639142440540541642638941037734734737642439938889
Percentage of EquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, mmc:ConsultingSegment



Period End2019-12-312018-12-312017-12-31
Value149148269
Percentage of EquityMethodInvestments34.351.666.4

us-gaap:OperatingSegments, mmc:RiskandInsuranceServicesSegment



Period End2019-12-312018-12-312017-12-31
Value1795760
Percentage of EquityMethodInvestments41.219.914.8

us-gaap:InvestmentType

mmc:PrivateInsuranceandConsulting



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value17018321921915561606363
Percentage of EquityMethodInvestments45.842.248.549.939.921.320.316.115.6

us-gaap:PrivateEquityFunds



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value97107827679766138
Percentage of EquityMethodInvestments26.124.728.618.820.321.915.742.7

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

mmc:AlexanderForbesGroupHoldingsLimited



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value105144138140149144153246286266268275289247266235230250301278
Percentage of EquityMethodInvestments28.333.230.531.938.450.251.762.967.565.766.266.167.863.564.962.366.366.571.069.7

us-gaap:EquitySecuritiesFvNi



Period End2020-03-312019-12-312019-09-302018-12-31
Value181919146
Percentage of EquitySecuritiesFvNi100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherAssets, us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302018-12-31
Value345133
Percentage of EquitySecuritiesFvNi16.721.126.391.1

us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherAssets, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302018-12-31
Value345133
Percentage of EquitySecuritiesFvNi16.721.126.391.1

us-gaap:InvestmentType

us-gaap:EquitySecurities



Period End2019-12-312018-12-31
Value19146
Percentage of EquitySecuritiesFvNi100.0100.0

us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValueAmount



Period End2020-03-312019-12-312019-09-302018-12-31
Value32674775
Percentage of EquitySecuritiesWithoutReadilyDeterminableFairValueAmount100.0100.0100.0100.0

us-gaap:EscrowDeposit



Period End2020-03-312019-03-312018-12-312018-03-31
Value0635900
Percentage of EscrowDeposit0.0100.00.00.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value6833343723231674152915071430132912451122
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanByPlanAssetCategories

us-gaap:CorporateDebtSecurities



Period End2019-12-312018-12-312017-12-31
Value0020
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue0.00.05.4

us-gaap:DefinedBenefitPlanEquitySecuritiesCommonStock



Period End2019-12-312018-12-312017-12-31
Value112
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue0.10.30.5

us-gaap:OtherInvestments



Period End2019-12-312018-12-312017-12-31
Value682333350
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue99.999.794.1

us-gaap:FairValueByLiabilityClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue

mmc:ContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value2392251851964545082681851611891702032472412322793023092832442062071511441331049281616377116108110119111106
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302009-12-31
Value116011001021946849792754714685632590546505468443424451421541518491485458460439416399372359345328304292265248236220212201166
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CustomerLists



Period End2019-12-312018-12-312017-12-312016-12-312016-06-302016-03-312015-12-312014-12-31
Value897639518392359372347391
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization81.580.782.083.884.782.582.480.6

us-gaap:CustomerRelationships



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value951897824765685639611580560518487453422392371347
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization82.081.580.780.980.780.781.081.281.882.082.583.083.683.883.782.4

us-gaap:OtherIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-31
Value2092031971811641531431341251141039383767265797494
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization18.018.519.319.119.319.319.018.818.218.017.517.016.416.216.315.317.517.619.4

us-gaap:FiniteLivedIntangibleAssetsGross



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302009-12-31
Value3823387438904029231322292083194819411906191017791796159413501379148614571377129211631177109311011079888887849806814762747746666642641656615562395
Percentage of FiniteLivedIntangibleAssetsGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CustomerLists



Period End2019-12-312018-12-312017-12-312016-12-312016-06-302016-03-312015-12-312014-12-31
Value34941970167213901229131212811000
Percentage of FiniteLivedIntangibleAssetsGross90.288.487.787.289.188.387.985.0

us-gaap:CustomerRelationships



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value3450349435263664204619701837171117001672167915811591139012021281
Percentage of FiniteLivedIntangibleAssetsGross90.290.290.690.988.588.488.287.887.687.787.988.988.687.289.087.9

us-gaap:OtherIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-31
Value373380364365267259246237241234231198205204148150174176177
Percentage of FiniteLivedIntangibleAssetsGross9.89.89.49.111.511.611.812.212.412.312.111.111.412.811.010.911.712.115.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:InterestRateFairValueHedgeAssetAtFairValue

mmc:OtherReceivables, us-gaap:FairValueInputsLevel2, us-gaap:FairValueMeasurementsRecurring



Period End2019-12-312018-12-312018-09-302017-12-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value88800022336
Percentage of InterestRateFairValueHedgeAssetAtFairValue100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

mmc:OtherReceivables, us-gaap:FairValueMeasurementsRecurring



Period End2019-12-312018-12-312018-09-302017-12-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value88800022336
Percentage of InterestRateFairValueHedgeAssetAtFairValue100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:LiabilitiesFairValueDisclosure

us-gaap:FairValueInputsLevel2, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value0000011600000000000000000252252253253256
Percentage of LiabilitiesFairValueDisclosure0.00.00.00.00.0100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0100.0100.0100.0100.0100.0

us-gaap:FairValueInputsLevel3, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value2392251851964545082681851611891702032472412322793023092832442062071511441331049263
Percentage of LiabilitiesFairValueDisclosure0.00.00.00.00.0437.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.057.152.841.136.424.6

us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value239225185196454624268185161189170203247241232279302309283244206207151396385357345319
Percentage of LiabilitiesFairValueDisclosure0.00.00.00.00.0537.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0157.1152.8141.1136.4124.6

us-gaap:CreditFacility, us-gaap:DebtInstrument

us-gaap:LineOfCredit

mmc:TermLoanFacility, mmc:A500MillionOneYearTermLoanand500MillionTwoYearTermLoan



Period End2020-03-31
Value1000
Percentage of LineOfCredit100.0

us-gaap:RevolvingCreditFacility, mmc:AmendedRevolvingCreditFacility



Period End2020-03-312019-09-30
Value10000
Percentage of LineOfCredit100.00.0

us-gaap:CreditFacility, us-gaap:SubsequentEventType

mmc:TermLoanFacility, us-gaap:SubsequentEvent



Period End2020-01-31
Value0.0
Percentage of LineOfCredit0.0

us-gaap:DebtInstrument

mmc:OtherDebtFacilities



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value0001001
Percentage of LineOfCredit0.00.00.00.00.00.00.0

us-gaap:CreditFacility, us-gaap:DebtInstrument

us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity

mmc:TermLoanFacility, mmc:A500MillionOneYearTermLoanFacility



Period End2020-01-31
Value500
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity100.0

mmc:TermLoanFacility, mmc:A500MillionTwoYearTermLoanFacility



Period End2020-01-31
Value500
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity100.0

us-gaap:CreditFacility, us-gaap:DebtInstrument, us-gaap:SubsequentEventType

mmc:TermLoanFacility, mmc:A500MillionOneYearTermLoanFacility, us-gaap:SubsequentEvent



Period End2020-01-31
Value500
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity100.0

mmc:TermLoanFacility, mmc:A500MillionTwoYearTermLoanFacility, us-gaap:SubsequentEvent



Period End2020-01-31
Value500
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity100.0

us-gaap:DebtInstrument, us-gaap:SubsequentEventType

mmc:April2020NewCreditFacility, us-gaap:SubsequentEvent



Period End2020-04-30
Value1000
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity0.0

us-gaap:DebtInstrument

us-gaap:LinesOfCreditCurrent

us-gaap:RevolvingCreditFacility



Period End2020-03-312019-12-31
Value10000
Percentage of LinesOfCreditCurrent100.00.0

us-gaap:LongTermDebtAndCapitalLeaseObligations



Period End2019-12-312019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value10741114725510551258135815522554755479547944954494449647484402442238253828337633793212261926212623270327052658266026632664266826702773277130263028303230343194
Percentage of LongTermDebtAndCapitalLeaseObligations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByMeasurementBasis

us-gaap:LongTermDebtFairValue

us-gaap:CarryingReportedAmountFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value112311074111429114595510
Percentage of LongTermDebtFairValue100.0100.0100.0100.0100.0

us-gaap:EstimateOfFairValueFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value120331195312666122315437
Percentage of LongTermDebtFairValue107.1111.3110.8106.798.7

us-gaap:LossContingencyEstimateOfPossibleLoss



Period End2020-03-312019-12-31
Value7365
Percentage of LossContingencyEstimateOfPossibleLoss100.0100.0

us-gaap:NumberOfCountriesInWhichEntityOperates



Period End2020-03-31
Value130.0
Percentage of NumberOfCountriesInWhichEntityOperates100.0

us-gaap:OperatingLeaseLiability



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value22322268229823281881
Percentage of OperatingLeaseLiability100.0100.0100.0100.0100.0

us-gaap:OperatingLeaseLiabilityCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value3343423413472910
Percentage of OperatingLeaseLiabilityCurrent100.0100.0100.0100.0100.00.0

us-gaap:OperatingLeaseLiabilityNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value189819261957198115900
Percentage of OperatingLeaseLiabilityNoncurrent100.0100.0100.0100.0100.00.0

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent



Period End2020-03-312019-03-31
Value0.03060.0312
Percentage of OperatingLeaseWeightedAverageDiscountRatePercent100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherAssetsFairValueDisclosure

us-gaap:OtherAssets, us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value138166157153145151153144146158143140134141140133132142136142140150150150144154146139
Percentage of OtherAssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherAssets, us-gaap:FairValueMeasurementsRecurring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value138166157153145151153144146158143140134141140133132142136142140150150150144154146139
Percentage of OtherAssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherIntangibleAssetsNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value2663277428693083146414371329123412561274132012331291112690795510351036
Percentage of OtherIntangibleAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherReceivablesGrossCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value561645575547372366467367389401311298278286318287318309295297285280258292300282219244
Percentage of OtherReceivablesGrossCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities

country:US, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value122
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities100.0100.0100.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-31
Value292827
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities2900.01400.01350.0

us-gaap:ForeignPlan, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value3343
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities300.0150.0200.00.0

us-gaap:ForeignPlan, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value6565
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities600.0250.0300.00.0

us-gaap:RestrictedCashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value202197193192186
Percentage of RestrictedCashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve

us-gaap:RestructuringAndRelatedCostCostIncurredToDate1

mmc:JardineLloydThompsonGroupplc, mmc:AcquisitionRelated



Period End2020-03-312019-12-31
Value80335
Percentage of RestructuringAndRelatedCostCostIncurredToDate1100.0100.0

us-gaap:RestructuringReserve



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312017-01-012016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value681025072111112838763656974749393717785937485869298109111124130135143170143145159181159169189211259222
Percentage of RestructuringReserve100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

mmc:JardineLloydThompsonGroupplc



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value534742740
Percentage of RestructuringReserve77.946.184.0102.80.0

us-gaap:BusinessAcquisition, us-gaap:RestructuringCostAndReserve

mmc:JardineLloydThompsonGroupplc, mmc:InformationTechnology



Period End2020-03-312019-12-312019-09-302018-12-31
Value4000
Percentage of RestructuringReserve5.90.00.00.0

mmc:JardineLloydThompsonGroupplc, mmc:LegalConsultingandOtherOutsideServices



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value300280
Percentage of RestructuringReserve4.40.00.038.90.0

mmc:JardineLloydThompsonGroupplc, mmc:RealEstateRelatedCosts



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value55900
Percentage of RestructuringReserve7.44.918.00.00.0

mmc:JardineLloydThompsonGroupplc, us-gaap:EmployeeSeverance



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value414233460
Percentage of RestructuringReserve60.341.266.063.90.0

us-gaap:RestructuringCostAndReserve

us-gaap:EmployeeSeverance



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-31
Value2451183773734343151514191532471215455778811121520361011172712174077
Percentage of RestructuringReserve35.350.036.051.465.865.251.849.423.823.120.325.720.334.45.69.114.116.15.45.95.87.67.17.37.28.99.211.114.021.27.07.610.714.97.510.119.029.7

us-gaap:OtherRestructuring



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312011-12-31
Value4451323538394044485055555961677073787080818591101103113118134154
Percentage of RestructuringReserve64.750.064.048.634.234.848.250.676.276.979.774.379.765.694.490.985.983.994.694.194.292.492.992.792.891.190.878.885.1

us-gaap:RevenueRemainingPerformanceObligation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value142105107186190221223239284
Percentage of RevenueRemainingPerformanceObligation100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Subsegments

mmc:MarshInsuranceGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value363933223032294824
Percentage of RevenueRemainingPerformanceObligation25.437.130.811.815.814.513.020.18.5

mmc:MercerConsultingGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value221104127323429486488450575
Percentage of RevenueRemainingPerformanceObligation155.699.0118.7173.7225.8219.9218.8188.3202.5

mmc:OliverWymanGroupConsultingGroup



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value242332228
Percentage of RevenueRemainingPerformanceObligation1.43.81.91.61.60.90.90.82.8

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber

us-gaap:PerformanceShares



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value650547.0698798.0690601.0722017.0678165.0868008.0961163.0730838.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RestrictedStockUnitsRSU



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value5443224815
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber915.8619.7586.8421.6362.6241.7442.31226.60.0

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

us-gaap:PerformanceShares



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value82.7570.3362.8254.6846.2537.5632.8731.32
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RestrictedStockUnitsRSU



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value87.876.4966.9756.452.5138.7432.0428.5825.43
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue106.1108.8106.6103.1113.5103.197.591.30.0

us-gaap:AwardType, us-gaap:PlanName

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized

us-gaap:EmployeeStock, mmc:EmployeeStockPurchasePlan1999



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value40403535353535
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized100.0100.0100.0100.0100.0100.0100.0

us-gaap:EmployeeStock, mmc:InternationalPlan



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value11111212121212
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized27.327.333.733.733.733.733.7

us-gaap:AwardType, us-gaap:PlanName

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant

us-gaap:EmployeeStock, mmc:EmployeeStockPurchasePlan1999



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value5511223
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant100.0100.0100.0100.0100.0100.0100.0

us-gaap:EmployeeStock, mmc:InternationalPlan



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value1122222
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant24.124.2184.2146.7121.0104.188.2

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:SharePrice

mmc:AlexanderForbesGroupHoldingsLimited



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312014-12-31
Value4.285.555.65.795.035.144.955.777.26.876.756.956.437.956.456.56.77.5
Percentage of SharePrice100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShortTermBorrowings



Period End2019-12-312018-12-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-03-312009-12-312008-12-31
Value1215314101026025925925926026026026189558558408
Percentage of ShortTermBorrowings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtInstrument

mmc:TermLoanFacility



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value50003003000
Percentage of ShortTermBorrowings0.00.00.00.00.0

us-gaap:ShortTermDebtType

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-06-302017-03-312016-03-312015-12-312015-06-302014-12-312014-03-312013-12-31
Value150015001500150025205001000
Percentage of ShortTermBorrowings0.0123.50.00.00.00.00.00.00.00.0

us-gaap:FairValueByMeasurementBasis

us-gaap:ShorttermDebtFairValue

us-gaap:CarryingReportedAmountFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value2409121511391633314
Percentage of ShorttermDebtFairValue100.0100.0100.0100.0100.0

us-gaap:EstimateOfFairValueFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value2416122911401665313
Percentage of ShorttermDebtFairValue100.3101.2100.1102.099.7

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-03-312008-12-312007-12-31
Value7451794377978337798675847538779780217442713170746619627267546705677166026343687268637133791582288043797571206846671366066580634462655940646567806687641564156043601458636039569457607853
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-03-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value-3374-3512-2990-2953-2892-3232-3124-3393
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-45.3-44.2-37.4-38.9-38.9-51.5-47.3-47.6

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value00141965
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest0.00.00.20.30.10.1

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-03-312008-12-312007-12-312006-12-31
Value-5847-5055-4931-4527-4590-4647-4488-4265-3905-4043-4560-4541-4837-5093-4289-4301-4097-4220-4122-3923-4090-3847-2895-2607-2708-2621-3213-3435-3379-3307-3005-3115-3023-3188-2333-2078-2183-2300-2138-2406-2246-2171-1836-2132-2098-351-1272
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-78.5-63.6-63.2-54.3-57.5-61.3-59.5-54.7-48.7-54.3-63.9-64.2-73.1-81.2-63.5-64.1-60.5-63.9-65.0-57.1-59.6-53.9-36.6-31.7-33.7-32.9-45.1-50.2-50.3-50.1-45.7-49.1-48.3-53.7-36.1-30.6-32.6-35.9-33.3-39.8-37.3-37.0-30.4-37.4-36.4-4.50.0

us-gaap:AccumulatedTranslationAdjustment



Period End2020-03-312019-12-312019-03-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value-2473-1543-1600-1694-1165-1880-1102-459
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-33.2-19.4-20.0-22.3-15.7-30.0-16.7-6.4

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302009-12-312008-12-31
Value746862796736681817771732682784783763733842812789777861851842837930922914909102810101002993110710761053101811561123109210501185115912111245
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest10.010.910.28.88.510.810.29.48.510.511.010.811.113.412.011.811.513.013.412.312.213.011.611.111.312.914.214.614.816.816.416.616.219.517.416.115.718.518.120.721.6

us-gaap:NoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-03-312008-12-312007-12-312006-12-31
Value15615017727277738581818385818780838192899589917982778270786773647071675758535847454337353534383123
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest2.11.92.33.31.01.01.11.01.01.11.21.11.31.31.21.21.41.31.51.31.31.11.00.91.00.91.11.01.11.01.11.11.11.00.90.80.90.70.70.70.60.60.60.60.70.40.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-03-312008-12-312007-12-312006-12-31
Value1549015199148111474114642143471419614131138121314013113129151260612388119531175111460113021092810768105151033510042989796209452915190368786862883718257805379497696768875287436723671877062703370137202723777325691
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest207.9191.4190.0176.8183.3189.2188.3181.2172.2176.6183.9182.6190.5197.5177.0175.3169.3171.2172.3156.7153.2144.9126.9120.3119.6118.5128.5132.0130.9130.6127.2130.2128.5133.8119.0113.4112.6115.9112.8118.9117.4120.0116.1126.5125.698.50.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-03-312008-12-312007-12-312006-12-31
Value-3655-3774-3617-3446-3385-3567-3587-3443-3210-3083-2851-2705-2531-2506-2366-2176-2022-1991-1970-1465-1051-925-797-614-421-515-467-385-321-447-493-483-411-595-640-536-327-514-448-491-509-806-915-1154-1223-1362-299
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-49.1-47.5-46.4-41.3-42.4-47.0-47.6-44.2-40.0-41.4-40.0-38.2-38.2-40.0-35.0-32.5-29.9-30.2-31.1-21.3-15.3-13.0-10.1-7.5-5.2-6.5-6.6-5.6-4.8-6.8-7.5-7.6-6.6-10.0-9.9-7.9-4.9-8.0-7.0-8.1-8.5-13.7-15.2-20.3-21.2-17.30.0

us-gaap:TreasuryStockShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-