AON


Line plots across dimensions of each concept
Tables

Table of contents



us-gaap:CommonStockValue

us-gaap:CommonStockParOrStatedValuePerShare

us-gaap:CommonStockSharesIssued
us-gaap:StatementEquityComponents

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:IncomeLossFromContinuingOperationsPerBasicShare

us-gaap:IncomeLossFromContinuingOperationsPerDilutedShare

us-gaap:Revenues
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:ProductOrService
us-gaap:StatementGeographical

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax

us-gaap:CostsAndExpenses
us-gaap:ConsolidatedEntities

us-gaap:OperatingIncomeLoss
us-gaap:ConsolidatedEntities

us-gaap:InterestExpense
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:OtherNonoperatingIncomeExpense
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:StatementEquityComponents

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:IncomeTaxExpenseBenefit
us-gaap:ConsolidatedEntities

us-gaap:IncomeTaxesPaidNet

us-gaap:ProfitLoss
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:StatementEquityComponents

us-gaap:ComprehensiveIncomeNetOfTax
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest
us-gaap:ConsolidatedEntities

us-gaap:Assets
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:Liabilities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:LiabilitiesAndStockholdersEquity
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:StockholdersEquity
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:AssetsCurrent
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:CashAndCashEquivalentsAtCarryingValue
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:ShortTermInvestments
us-gaap:ConsolidatedEntities

us-gaap:AccountsReceivableNetCurrent
us-gaap:ConsolidatedEntities

us-gaap:OtherAssetsCurrent
us-gaap:ConsolidatedEntities

us-gaap:PropertyPlantAndEquipmentGross
us-gaap:PropertyPlantAndEquipmentByType

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:PropertyPlantAndEquipmentNet
us-gaap:ConsolidatedEntities

us-gaap:LongTermInvestments

us-gaap:Goodwill
us-gaap:BusinessAcquisition
us-gaap:ConsolidatedEntities

us-gaap:IntangibleAssetsNetExcludingGoodwill
us-gaap:ConsolidatedEntities
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:DeferredTaxAssetsLiabilitiesNet

us-gaap:OtherAssetsNoncurrent
us-gaap:ConsolidatedEntities

us-gaap:LiabilitiesCurrent
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:DebtCurrent
us-gaap:ConsolidatedEntities

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:OtherAccruedLiabilitiesCurrent

us-gaap:AccruedIncomeTaxesCurrent

us-gaap:OtherLiabilitiesCurrent
us-gaap:ConsolidatedEntities

us-gaap:LongTermDebtNoncurrent
us-gaap:ConsolidatedEntities
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent

us-gaap:MinorityInterest
us-gaap:ConsolidatedEntities

us-gaap:OtherLiabilitiesNoncurrent
us-gaap:ConsolidatedEntities

us-gaap:StockholdersEquity
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:CommonStockValue

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:NetCashProvidedByUsedInOperatingActivities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:NetCashProvidedByUsedInInvestingActivities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:NetCashProvidedByUsedInFinancingActivities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:NetCashProvidedByUsedInOperatingActivities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:ProfitLoss
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:StatementEquityComponents

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

us-gaap:NetCashProvidedByUsedInInvestingActivities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment
us-gaap:ConsolidatedEntities

us-gaap:NetCashProvidedByUsedInFinancingActivities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:ProceedsFromIssuanceOfLongTermDebt
us-gaap:ConsolidatedEntities

us-gaap:RepaymentsOfLongTermDebt
us-gaap:ConsolidatedEntities

us-gaap:RepaymentsOfLongTermDebt
us-gaap:ConsolidatedEntities
us-gaap:DebtInstrument
us-gaap:DebtInstrumentInterestRateStatedPercentage
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
us-gaap:LongtermDebtType

us-gaap:EffectiveIncomeTaxRateContinuingOperations
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod

us-gaap:ShareBasedCompensation

us-gaap:DeferredTaxLiabilities

us-gaap:DeferredTaxAssetsNet

us-gaap:UnrecognizedTaxBenefits

us-gaap:DeferredTaxAssetsValuationAllowance

us-gaap:OperatingLeaseRightOfUseAsset
us-gaap:ConsolidatedEntities

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

aon:AccountsReceivableAllowanceForCreditLossForeignCurrencyTranslationAndOther

aon:AccountsReceivableAllowanceForCreditLossWriteoffNetOfRecoveries
us-gaap:CapitalizedContractCost
aon:CapitalizedContractCostAdditions
us-gaap:CapitalizedContractCost
aon:CapitalizedContractCostForeignCurrencyAndOtherAdjustmentsNet
us-gaap:ConsolidatedEntities
aon:EquityEarningsFromSubsidiaries
us-gaap:ConsolidationItems
us-gaap:ConsolidatedEntities
aon:EquityOtherComprehensiveIncomeLossFromSubsidiaries
us-gaap:ConsolidationItems

aon:GainLossOnSaleofBusinessAndInvestmentsNet

aon:IncomeLossBeforeEquityEarningsOfSubsidiaries
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

aon:IncomeLossFromContinuingOperationsBeforeIncomeTaxes
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aon:IncomeLossfromDiscontinuedOperationsExcludingGainLossonDisposalNetofTaxIncludingPortionAttributabletoNoncontrollingInterest

aon:IncreaseDecreaseInFiduciaryLiabilities

aon:IncreaseDecreaseInFiduciaryReceivables
us-gaap:ConsolidatedEntities
aon:IntercompanyInterestExpenseIncome
us-gaap:ConsolidatedEntities
aon:IntercompanyOtherIncomeExpenseNet
us-gaap:DisposalGroupClassification
aon:NumberOfDispositions

aon:OtherGeneralExpenses
us-gaap:ConsolidatedEntities

aon:OtherNonoperatingIncomeExpenseOther

aon:PaymentsForProceedsFromMarketableSecurities
us-gaap:ConsolidatedEntities

aon:ProceedsPaymentTowardsIssuanceofSharesUnderIncentiveandSharebasedCompensationPlansNetofPaymentsRelatedtoTaxWithholdingforSharebasedCompensation
us-gaap:ConsolidatedEntities

aon:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodTax
us-gaap:StatementEquityComponents
us-gaap:RestructuringCostAndReserve, us-gaap:RestructuringPlan
aon:RestructuringandRelatedCostIncurredContractTerminationCosts
us-gaap:AwardType
aon:ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuable
us-gaap:ShortTermDebtType
aon:ShortTermDebtAverageOutstandingAmountWeightedAverageInterestRate
us-gaap:ShareRepurchaseProgram
aon:TreasuryStockAcquiredAdditionalTransactionCosts
us-gaap:ShareRepurchaseProgram
aon:TreasuryStockValueAcquiredCostMethodIncludingAssociatedAcquisitionCosts

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents

us-gaap:AllocatedShareBasedCompensationExpense
us-gaap:AwardType

us-gaap:AmortizationOfIntangibleAssets
us-gaap:ConsolidatedEntities

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
us-gaap:CapitalizedContractCost
us-gaap:CapitalizedContractCostAmortization

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:ContractWithCustomerLiabilityRevenueRecognized

us-gaap:DeferredIncomeTaxesAndTaxCredits
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

us-gaap:DefinedBenefitPlanContributionsByEmployer
us-gaap:RetirementPlanSponsorLocation
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:Depreciation
us-gaap:ConsolidatedEntities
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeGainLossOnDerivativeNet
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DiscontinuedOperationTaxEffectOfDiscontinuedOperation
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationOperatingExpense

us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal

us-gaap:DividendsCommonStockCash
us-gaap:StatementEquityComponents

us-gaap:EffectOfExchangeRateOnCashAndCashEquivalents
us-gaap:ConsolidatedEntities

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax

us-gaap:GainLossOnSaleOfInvestments

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTax
us-gaap:ConsolidatedEntities
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare

us-gaap:IncomeLossFromEquityMethodInvestments

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities

us-gaap:IncreaseDecreaseInAccruedIncomeTaxesPayable

us-gaap:IncreaseDecreaseInClientFundsHeld
us-gaap:ConsolidatedEntities
us-gaap:IncreaseDecreaseInDueToAffiliates
us-gaap:ConsolidationItems

us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations

us-gaap:IncreaseDecreaseInReceivables

us-gaap:IncreaseDecreaseInRestructuringReserve

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InformationTechnologyAndDataProcessing
us-gaap:ConsolidatedEntities

us-gaap:InterestPaidNet

us-gaap:InvestmentIncomeInterestAndDividend
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:LaborAndRelatedExpense
us-gaap:ConsolidatedEntities
us-gaap:LitigationCase
us-gaap:LossContingencyDamagesSoughtValue
us-gaap:LitigationCase, us-gaap:LitigationStatus
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:NotionalAmountOfNonderivativeInstruments

us-gaap:NumberOfBusinessesAcquired

us-gaap:NumberOfReportableSegments

us-gaap:OccupancyNet
us-gaap:ConsolidatedEntities
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
us-gaap:StatementEquityComponents
us-gaap:DerivativeInstrumentRisk
us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax
us-gaap:IncomeStatementLocation

us-gaap:OtherComprehensiveIncomeLossNetOfTax
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest
us-gaap:ConsolidatedEntities

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax
us-gaap:ConsolidatedEntities
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
us-gaap:ConsolidatedEntities
us-gaap:StatementEquityComponents

us-gaap:PaymentsForRepurchaseOfEquity
us-gaap:ConsolidatedEntities

us-gaap:PaymentsOfDividendsCommonStock
us-gaap:ConsolidatedEntities

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired
us-gaap:ConsolidatedEntities

us-gaap:PaymentsToAcquireOtherInvestments
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:PaymentsToMinorityShareholders
us-gaap:ConsolidatedEntities

us-gaap:PensionExpense

us-gaap:ProceedsFromDivestitureOfBusinessesNetOfCashDivested
us-gaap:ConsolidatedEntities

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities
us-gaap:ConsolidatedEntities

us-gaap:ProceedsFromSaleAndMaturityOfOtherInvestments
us-gaap:ConsolidatedEntities

us-gaap:ProvisionForDoubtfulAccounts

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax
us-gaap:StatementEquityComponents

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
us-gaap:StatementEquityComponents
us-gaap:RestructuringCostAndReserve, us-gaap:RestructuringPlan
us-gaap:RestructuringAndRelatedCostIncurredCost
us-gaap:RestructuringPlan

us-gaap:RestructuringCharges
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
us-gaap:ShortTermDebtType
us-gaap:ShorttermDebtAverageOutstandingAmount
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation
us-gaap:StatementEquityComponents
us-gaap:ShareRepurchaseProgram
us-gaap:TreasuryStockAcquiredAverageCostPerShare
us-gaap:ShareRepurchaseProgram, us-gaap:SubsequentEventType
us-gaap:ShareRepurchaseProgram
us-gaap:TreasuryStockSharesAcquired
us-gaap:ShareRepurchaseProgram, us-gaap:SubsequentEventType
us-gaap:StatementEquityComponents

us-gaap:TreasuryStockValueAcquiredCostMethod
us-gaap:ShareRepurchaseProgram
us-gaap:ShareRepurchaseProgram, us-gaap:SubsequentEventType
us-gaap:StatementEquityComponents
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
aon:BasisMoneyMarketFundsAndHighlyLiquidSecuritiesFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:IncomeTaxAuthority
aon:CapitalLossCarryforwards

aon:CashandCashEquivalentsandShortTermInvestments

aon:DeferredTaxAssetsAccruedInterest

aon:DeferredTaxAssetsLeaseGuarantees

aon:DeferredTaxAssetsNetOperatingAndCapitalLossCarryforwardsAndTaxCreditCarryforwards

aon:DeferredTaxLiabilitiesIntangibleAssetsAndPropertyPlantAndEquipment

aon:DeferredTaxLiabilitiesOtherAccruedExpenses
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
aon:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationUnderlyingPriceInflation
us-gaap:RetirementPlanSponsorLocation
aon:DefinedBenefitPlanEstimatedEmployerContributionsForCurrentFiscalYear
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
aon:DefinedBenefitPlanMarketRelatedValue

aon:DistributableReservesAvailableAmount

aon:EmployeerelatedLiabilitiesNoncurrent

aon:FiduciaryAssets
us-gaap:ConsolidatedEntities

aon:FiduciaryAssetsPremiumTrustBalances

aon:FiduciaryLiabilities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:IncomeTaxAuthority
aon:InterestCarryforward
us-gaap:ConsolidatedEntities
aon:InvestmentsInSubsidiaries
us-gaap:ConsolidationItems
us-gaap:CreditFacility, us-gaap:LongtermDebtType
aon:LineofCreditFacilityMaximumBorrowingCapacityIncreaseDecrease
us-gaap:DebtInstrument, us-gaap:ShortTermDebtType, us-gaap:SubsequentEventType

aon:OperatingLeaseAndFinanceLeaseLiabilitiesNoncurrent

aon:OperatingLeaseAndFinanceLeaseLiabilityCurrent

aon:OtherTaxAssetsCurrent

aon:PropertyPlantAndEquipmentAndOperatingLeaseRightOfUseAssetAfterAccumulatedDepreciationandAmortization
us-gaap:StatementGeographical

aon:RestrictedCashOperatingFunds
us-gaap:AwardType
aon:UnamortizedExpenseOnPerformanceBasedPlans
us-gaap:TitleOfIndividual, us-gaap:SubsequentEventType
aon:UnusualOrInfrequentItemTemporaryCompensationReductionPercentage

us-gaap:AccruedIncomeTaxesNoncurrent

us-gaap:AdditionalPaidInCapitalCommonStock

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent
aon:CumulativeEffectPeriodOfAdoption
us-gaap:AdjustmentsForNewAccountingPronouncements, aon:CumulativeEffectPeriodOfAdoption
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisitionPercentageOfVotingInterestsAcquired
us-gaap:CapitalizedContractCost
us-gaap:CapitalizedContractCostNet

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:ContractWithCustomerAssetNetCurrent

us-gaap:ContractWithCustomerAssetNetNoncurrent

us-gaap:ContractWithCustomerLiabilityCurrent

us-gaap:ContractWithCustomerLiabilityNoncurrent

us-gaap:CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
us-gaap:AdjustmentsForNewAccountingPronouncements
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:SubsequentEventType
us-gaap:StatementEquityComponents
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
us-gaap:DebtInstrumentFaceAmount

us-gaap:DebtLongtermAndShorttermCombinedAmount
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
us-gaap:ShortTermDebtType

us-gaap:DeferredIncomeTaxAssetsNet
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:DeferredIncomeTaxLiabilitiesNet
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems

us-gaap:DeferredTaxAssetsDeferredIncome

us-gaap:DeferredTaxAssetsGross

us-gaap:DeferredTaxAssetsInvestments

us-gaap:DeferredTaxAssetsOther

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther

us-gaap:DeferredTaxLiabilitiesOther

us-gaap:DeferredTaxLiabilitiesTaxDeferredIncome

us-gaap:DeferredTaxLiabilitiesUndistributedForeignEarnings

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

us-gaap:DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent
us-gaap:ConsolidatedEntities
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:Range, us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
us-gaap:Range, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:Range, us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanFairValueOfPlanAssets
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanFundedStatusOfPlan
us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanWeightedAverageAssetAllocations
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:DerivativeAssets
us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:BalanceSheetLocation
us-gaap:DerivativeFairValueOfDerivativeAsset
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:HedgingDesignation
us-gaap:BalanceSheetLocation
us-gaap:DerivativeFairValueOfDerivativeLiability
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:HedgingDesignation
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:DerivativeLiabilities
us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeNotionalAmount
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:HedgingDesignation

us-gaap:DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
us-gaap:ConsolidatedEntities
us-gaap:DueFromRelatedPartiesCurrent
us-gaap:ConsolidationItems
us-gaap:ConsolidatedEntities
us-gaap:DueFromRelatedPartiesNoncurrent
us-gaap:ConsolidationItems
us-gaap:ConsolidatedEntities
us-gaap:DueToRelatedPartiesCurrent
us-gaap:ConsolidationItems
us-gaap:ConsolidatedEntities
us-gaap:DueToRelatedPartiesNoncurrent
us-gaap:ConsolidationItems

us-gaap:FinanceLeaseLiabilityNoncurrent

us-gaap:FinanceLeaseRightOfUseAsset

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsGross
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:DisposalGroupClassification, us-gaap:GuaranteeObligationsByNature, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:GuaranteeObligationsCurrentCarryingValue

us-gaap:GuaranteeObligationsMaximumExposure
us-gaap:DisposalGroupClassification, us-gaap:GuaranteeObligationsByNature, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:IncomeTaxesReceivableNoncurrent

us-gaap:LettersOfCreditOutstandingAmount
us-gaap:CreditFacility
us-gaap:LineOfCredit
us-gaap:CreditFacility
us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity
us-gaap:CreditFacility, us-gaap:LongtermDebtType
us-gaap:DebtInstrument, us-gaap:ShortTermDebtType
us-gaap:DebtInstrument, us-gaap:ShortTermDebtType, us-gaap:SubsequentEventType
us-gaap:ShortTermDebtType
us-gaap:StatementGeographical, us-gaap:ShortTermDebtType

us-gaap:LongTermDebtFairValue
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis
us-gaap:LitigationCase, us-gaap:LossContingenciesByNatureOfContingency
us-gaap:LossContingencyEstimateOfPossibleLoss
us-gaap:LossContingenciesByNatureOfContingency
us-gaap:Range

us-gaap:OperatingLeaseLiability

us-gaap:OperatingLeaseLiabilityNoncurrent
us-gaap:ConsolidatedEntities
us-gaap:IncomeTaxAuthority
us-gaap:OperatingLossCarryforwards

us-gaap:OtherAccruedLiabilitiesNoncurrent

us-gaap:OtherAssetsMiscellaneousCurrent

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

us-gaap:PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent
us-gaap:ConsolidatedEntities
us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities

us-gaap:PrepaidExpenseCurrent

us-gaap:RestrictedCashAndInvestmentsCurrent
us-gaap:RestructuringCostAndReserve, us-gaap:RestructuringPlan
us-gaap:RestructuringAndRelatedCostCostIncurredToDate1
us-gaap:RestructuringPlan

us-gaap:RestructuringReserve
us-gaap:RestructuringPlan

us-gaap:SecuredDebtCurrent
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
us-gaap:ShortTermDebtType
us-gaap:ShortTermBorrowings

us-gaap:ShorttermDebtFairValue
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis
us-gaap:ShareRepurchaseProgram
us-gaap:StockRepurchaseProgramAuthorizedAmount1

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:StatementEquityComponents

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1
us-gaap:StatementEquityComponents

us-gaap:TaxCutsAndJobsActOf2017IncompleteAccountingTransitionTaxForAccumulatedForeignEarningsProvisionalLiabilityNoncurrent

us-gaap:UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued

us-gaap:UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate

Tables

  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:CommonStockValue ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁██████████22222222223333333333333333333333386386386386386386363363363363NANANA
us-gaap:CommonStockParOrStatedValuePerShare ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁██████████0.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.011.01.01.01.01.01.01.01.01.01.0NANANA
us-gaap:CommonStockSharesIssued ▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃▄▄▄▄▄▄▅▅▅██████▇▇▇▇234232234235240240241243245247250255262262263265264269273279281280285290296300301307301310318322386386386386386385362362362362NANANA
 us-gaap:CommonStockSharesIssued us-gaap:StatementEquityComponents us-gaap:CommonStockIncludingAdditionalPaidInCapital▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▃▂▃▃▃▃▃▃▄▄▄▄▄▅▅▅▅██231232234235240240241243245247250255262262263265264269273279281280285290296300301307309310318322386386NANANA385NANANA362NANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding 234NA239242243NA245247250NA257262267NA269269273NA283286287NA296301307NA312317320NA331335336NA336342345NA282282283NA292292292
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic 233NA236240242NA244246248NA255262264NA267268271NA280284284NA292298303NA309313316NA327332332NA332337339NA278278275NA283285284
us-gaap:EarningsPerShareBasic █▄▃▄▇▄▂▂▆▁▃▇▃▅▄▃▄▆▃▂▄▄▃▃▃3.311.590.941.152.721.420.60.22.39-0.080.722.931.11.71.151.011.162.09999999999999961.050.631.151.61.061.021.07NA0.830.770.820.950.620.740.720.850.590.760.720.680.520.550.650.710.420.520.99
us-gaap:EarningsPerShareDiluted █▄▃▄▇▄▂▂▆▁▃▇▃▅▄▃▄▅▃▂▄▄▃▃▃3.291.580.931.142.71.410.60.192.37-0.070.722.931.091.681.141.011.152.081.040.621.141.561.041.011.06NA0.820.760.820.930.620.730.710.830.590.750.710.670.510.540.630.690.410.510.96
us-gaap:IncomeLossFromContinuingOperationsPerBasicShare █▅▃▄▇▄▃▂▆▁▃▁▃▅▄▄▄▆▃▃▄▅▄▃▄▄▃▃▃▃▃▃▃▃▃▃▃▃▂▃▃▂▂▂▃3.311.590.941.152.721.140.610.192.370.040.74-0.20.951.71.191.121.22.121.050.631.151.61.061.021.071.160.830.770.820.950.620.740.720.840.590.760.720.680.520.640.650.510.410.520.81
us-gaap:IncomeLossFromContinuingOperationsPerDilutedShare █▅▃▄▇▄▃▂▆▁▃▁▃▅▄▄▄▆▄▃▄▅▃▃▄▄▃▃▃▃▃▃▃▃▃▃▃▃▂▃▃▂▂▂▃3.291.580.931.142.71.130.610.192.350.040.73-0.20.941.681.181.111.192.091.050.621.141.561.041.011.061.140.820.760.820.930.620.730.710.820.590.750.710.670.510.630.630.490.40.50.79
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:Revenues █▆▄▅▇▆▄▅▇▆▄▄▄█▅▆▆█▅▆▆█▆▆▆█▆▆▆▇▅▆▆▇▅▆▅▆▁▁▂▂▁▁▁321928852379260631432770234925613090290923402368238132622746276627923288274228052847329928802919294732092794289729153115273728212841299427232811275929091801189819042073179418821846
 us-gaap:Revenues us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries█▅▁▃▇▄▁▃▇▆▁▁321928852379260631432770234925613090290923402368NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ConsolidationItems,us-gaap:ProductOrService us-gaap:OperatingSegments,aon:DataSolutions397NA4844194201105501431424-126491389386-216466405395NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ConsolidationItems,us-gaap:ProductOrService us-gaap:OperatingSegments,aon:Health502NA2793174861596278309451538293312372532265281292NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ConsolidationItems,us-gaap:ProductOrService us-gaap:OperatingSegments,aon:PCAdvisory1146NA1057116711184652102911661184122691710429841094884990961NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ConsolidationItems,us-gaap:ProductOrService us-gaap:OperatingSegments,aon:Reinsurance848NA2914207881563279380742359355344371329329332371NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ConsolidationItems,us-gaap:ProductOrService us-gaap:OperatingSegments,aon:Retirement331NA2712863361865263277294913289285268913260275259NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:StatementGeographical aon:EuropeMiddleEastAndAfrica978NA2835011009NA399493979NANANANANANANANANANANANANANANANANANANANANANANANANANANANANA393412NANA409438NA
 us-gaap:Revenues us-gaap:StatementGeographical country:GB█▂▄▅▇▅▁▅█500292358400452394264413484NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:StatementGeographical country:US▃█▃▂▂▃▃▁▁122715001209114611611221121511251116NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax ▂▂▁▂▂█▁▂▂▂▁▁▁▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁3219288523792606314310770234925613090290923402368238132622746276627923288274228052847329928802919294732092794289729153115273728212841299427232811275929091801189819042073179418821846
us-gaap:CostsAndExpenses ▃▅▁▃▄▄▂▇▄▅▂▆▁█▄▅▄▇▄▆▅█▆▆▆2186236120192193227122712087257722912420207524862038269423242361234225712329252824062664246324742478NA243025152505NA239824272439NA238223772363NA153816301631NA160016621480
 us-gaap:CostsAndExpenses us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries▃▆▁▃▅▅▂█▅▄▂█215423481998214922432256207824812270224220392486NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OperatingIncomeLoss █▅▄▄▇▅▃▂▇▅▃▁▄▅▄▄▄▆▄▃▄▆▄▄▅▅▄▄▄▅▄▄▄▄▄▄▄▄▃▃▃▃▃▃▄1033524360413872499262-16799489265-118343568422405450717413277441635417445469515364382410461339394402435341434396422263268273241194220366
 us-gaap:OperatingIncomeLoss us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries█▅▄▄▇▅▃▂▇▆▃▁106553738145790051427180820667301-118NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:InterestExpense █▇▇▆▅▄▄▄▄▅▄▅▄▄▄▅▄▄▅▄▃▄▃▃▁83807877727069697071707170707073696872686567656558NA534852NA575759NA606363NA503334NA322629
 us-gaap:InterestExpense us-gaap:ConsolidatedEntities aon:AonCorporation39NANANA28NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:InterestExpense us-gaap:ConsolidatedEntities aon:AonGlobalHoldingsLimited11NANANA24NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:InterestExpense us-gaap:ConsolidatedEntities aon:AonUK54NANANA46NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherNonoperatingIncomeExpense 29NA260NA1-3-1520-5-5-10-279018-5281421035-21NA3969NA-9120NA7-2317NA-957NA1314-1
 us-gaap:OtherNonoperatingIncomeExpense us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries72NA7248NA71913NA-612NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax ▂▇▃▅▇▄▅▁█▅█▆▇▃▅▅▅▅▃▇▂▃▂▆▆-397196-212-103133-181-50-460247-4424344147-268-89-59-79-66-229175-322-279-3187416NA155-58-174NA164-197104NANANANANANANANANANANANA
 us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax us-gaap:ConsolidationItems srt:ConsolidationEliminations▃▁█▂▄▅▃▇▃▃▃▁1-922-728-218-300-10NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax us-gaap:StatementEquityComponents us-gaap:NoncontrollingInterest-2NA-4NA22-3-6327-51NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest █▅▃▄▇▄▃▂▆▂▃▁▄▅▄▄▄▆▄▃▄▅▄▄▄7923822292876762841555760417196-43265384314280327590303188341467315313336NA264252272307210255249280208265253242147184186162131153235
 us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries█▄▄▄▇▄▂▃▆▃▂▁1046553480495910587288370851432313162NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeTaxExpenseBenefit ▅▄▄▄▅▅▃▁▄█▃▁▃▄▄▄▄▄▄▃▄▄▄▄▄18959565612613739-1441143894-143062485574112492680114756778NA899096NA649697NA8487103NA616061NA4757108
 us-gaap:IncomeTaxExpenseBenefit us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries▇▄▄▅▆▆▅▁▅█▄▁25610593120173218114-9115731493-72NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeTaxesPaidNet ▁▁▁▂▁▁▁▂▁▄█▁▁▁▁▁▁▁▁▁▁▁▁▂▁5374821643363671495832874650586564484169627246577613866NANANA148NANANA40NANANA36NANANA10NANANA53
us-gaap:ProfitLoss █▄▃▄▇▄▂▂▆▁▃█▄▅▄▄▄▆▄▃▄▅▄▄▄▄▃▃▃▄▃▃▃▄▃▃▃▃▂▂▃▃▂▂▄79138222828767635315358610-12192778305459314280327590303188341467315313336360264252272307210254249280208267255241147158186218134155285
 us-gaap:ProfitLoss us-gaap:ConsolidatedEntities aon:AonCorporation604NANANA513NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ProfitLoss us-gaap:ConsolidatedEntities aon:AonGlobalHoldingsLimited605NANANA600NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ProfitLoss us-gaap:ConsolidatedEntities aon:AonIreland773NANANA0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ProfitLoss us-gaap:ConsolidatedEntities aon:AonUK773NANANA661NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ProfitLoss us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries▆▃▃▄█▄▁▃█▂▂█10454584435221423553-783861439133931514NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ProfitLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings772NA22227765934514748594-19185769291502307272315584295178328459309304325NANANA261NANANA238NANANA246NANANA178NANANANA
us-gaap:ComprehensiveIncomeNetOfTax ▅▅▃▄█▃▃▁█▂▅█▅▅▄▄▃▆▃▅▃▂▃▅▅396371291808286839-285900-103450842453383236260286147836935-1579406379NA42720996NA38653369NA-20216203NA36463-152NA202412NA
 us-gaap:ComprehensiveIncomeNetOfTax us-gaap:ConsolidatedEntities aon:AonCorporation234NANANA652NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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 us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:ConsolidatedEntities aon:AonCorporation604NANANA513NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:ConsolidatedEntities aon:AonGlobalHoldingsLimited605NANANA600NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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 us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries▆▃▃▄█▄▁▃█▂▂█10264504375121406545-843761423126861505NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:NetIncomeLossAttributableToNoncontrollingInterest █▃▃▄▇▃▃▄▆▃▃▄▆▃▃▃▅▃▃▄▅▃▃▄▄▂▃▄▄▁▃▃▄▁▄▄▄▄▁▂▃█▆▃▂19861017861016779147781268101386911581111268113109910358201465
 us-gaap:NetIncomeLossAttributableToNoncontrollingInterest us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries█▂▁▃▇▂▁▃▆▂▂▃19861017861016779NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:Assets ▇▆▅▆▆▄▃▄▅▃▃▄▄▄▃▄▄▄▄▆▅▆▆█▇▇▆▇▇▇▆▇▇▆▆▇▆▆▁▂▁▁302822940528167298072913526422256022721727847260882592427189269822661525252266932681327164272062920328389297722882731776300773025129305300623002930486295093080730271295522874530496298022898223358239562295922958NANANA
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us-gaap:LiabilitiesAndStockholdersEquity ▇▆▅▆▆▄▃▄▅▃▃▄▄▄▃▄▄▄▄▆▅▆▆█▇▇▆▇▇▇▆▇▇▆▆▇▆▆▁▂▁▁302822940528167298072913526422256022721727847260882592427189269822661525252266932681327164272062920328389297722882731776300773025129305300623002930486295093080730271295522874530496298022898223358239562295922958NANANA
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  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:AssetsCurrent █▆▅▇▆▄▂▄▅▃▃▅▅▂▁▃▃▃▃▅▄▅▄█▆▆▅▆▆▆▅▇▆▅▄▆▅▄▄▅▃▃173451647615317167451591914372133481486015115136771426715602153931314612471138011404113972139201565514999158231475517711161731633015574163931625716382157021705616207155051450015931152111451914612154971426813989NANANA
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us-gaap:CashAndCashEquivalentsAtCarryingValue ▇█▆▅▆▆▄▄▆█▇▇▄▄▄▄▄▃▃▃▃▃▃▃▂▄▃▂▃▂▂▂▂▂▂▂▇▃▂▂▄▁▅▅▄690790602581600656484487597756749684433431483438465384398367378374382418338477369266408291290286323272295300682346335260422217580537501
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us-gaap:AccountsReceivableNetCurrent █▆▅▇▇▄▄▅▆▃▁▂▂▄▃▃▄▄▃▄▄▅▄▅▅▅▄▅▅▆▅▆▆▆▄▅▄▄▁▁▁▁355431122866322732422760265629923053247820682191210325892391251625912734245326842672281526302803288028962666283828843101295930753164318327452785265027012086199419832052NANANA
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  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:PropertyPlantAndEquipmentGross NA1780NANANA1733NANANA1733NANANA2325NANANA2381NANANA2311NANANA2289NANANA2189NANANA1971NANANA1877NANANA1489NANANA
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us-gaap:LiabilitiesCurrent █▆▅▆▅▃▃▄▄▃▂▃▃▂▁▃▃▃▄▅▄▅▄▇▆▆▆▆▆▆▄▆▅▄▃▄▃▃▂▄▃▃171111557114851154811453713296126431384313658127551247413375129701249511366126971279313086135411483914116150141385616040155811541115191151951526115350139541520014252137601276513987132591294911819141381277612640NANANA
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 us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries▁▁▁▂▁█▁▂139316751705205717621016618613040NA3913NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherAccruedLiabilitiesCurrent ▆▅▅▅▅▆██▄▄▄▄▃▃▄▃▃▂▃▃▃▂▂▂▁▁572513537504516602706723479420421447378402442372402331401394364314281307261247NANANA241NANANANANANANANANANANANANANANA
us-gaap:AccruedIncomeTaxesCurrent ▂▁▂▂▂▁▁▁▂▂▄█▁▁▁▁▁▁▁▁▁▁▁▂▂▂196931521331588316251641395371254577874676194824896696115140184NANANA155NANANANANANANANANANANANANANANA
us-gaap:OtherLiabilitiesCurrent ▅▄▄▅▅▄▄▄▄▃▅█▃▃▄▃▃▃▃▃▃▃▃▄▄▃▃▃▃▃▃▃▃▃▃▂▂▂▁▁▁▁12771086116311971220936988112197287012892078773873929872902820811845865788853957967906764769795831801733739753676618604584383350334260NANANA
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us-gaap:LongTermDebtNoncurrent ▇█▇█▇▇▇▇▇▇▇▆▆▇▇▇▇▆▅▅▅▅▅▆▄▄▃▄▄▄▄▄▄▄▅▅▅▄▃▁▂▂622766276120674059905993566556595697566756625631561058695910590759025175479948244710479948405155366936863352401237703713411140984168415544154479440940143146160120131998NANANA
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us-gaap:MinorityInterest █▆▅▆▇▅▄▅▇▄▅▄▅▃▄▄▄▃▃▃▄▄▃▃▄▂▃▃▃▁▃▃▃▁▂▅▄▃▂▂▃▂917469778768667384657266725760626657595866605759605056595443565858424667645552505552NANANA
 us-gaap:MinorityInterest us-gaap:ConsolidatedEntities srt:NonGuarantorSubsidiaries█▃▂▄▇▂▁▃9174697787686673NA65NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherLiabilitiesNoncurrent ▂▂▂▂▃▃▃▃▃▃▂▂▁▂▁▁▂▁▃▄▄▂▆▅▄▂▅▅▅▃▅▅▅▃███▄▂▃▂▂930877953924973109710901088110511028468587338447597678387691091114011318741422128912489321399134013381036132613321363102417431792179811548761023943871NANANA
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  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:StockholdersEquity ▁▁▁▂▃▂▂▃▄▃▄▄▄▄▄▄▄▅▅▅▅▆▆▇▇█▇▇▇▇████████▄▄▄▄316933753492383647754151426245455301458351755487575454755434549952816106588363986365657172157700794681457534755975797762830581528358807882338398842382515792542854025379NANANA
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us-gaap:CommonStockValue ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁██████████22222222223333333333333333333333386386386386386386363363363363NANANA
us-gaap:RetainedEarningsAccumulatedDeficit ▁▁▁▁▂▂▂▂▂▂▃▃▃▃▃▃▃▄▄▄▄▄▄▄▅▅▅▅▅▅▆▆███▇▇▇▇▇▇▇145512541436166925552093204222952747230229143574393438073702378436004117401544054612460547184982540357315507580558445933617963028770859483778233803978617700760575007335NANANA
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us-gaap:NetCashProvidedByUsedInOperatingActivities ▄▆▇▄▂▇▆▄▃▄▁▄▄▇▇▅▄█▇▃▃▇▆▄▂33867280228774711562273140381-147260240851711491273934710229136759550344-11NANANA54NANANA-15NANANA582NANANA464NANANA553
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us-gaap:NetCashProvidedByUsedInFinancingActivities █▅▄▇▇▆▆▇▅▅▄▁▇▆▆▅█▃▅▇▇▆▇▇▆82-525-736-92-140-444-457-135-663-617-878-1512-258-271-371-640-4-979-582-33-95-430-254-189-260NANANA120NANANA-166NANANA34NANANA17NANANA13
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us-gaap:ProfitLoss █▄▃▄▇▄▂▂▆▁▃█▄▅▄▄▄▆▄▃▄▅▄▄▄▄▃▃▃▄▃▃▃▄▃▃▃▃▂▂▃▃▂▂▄79138222828767635315358610-12192778305459314280327590303188341467315313336360264252272307210254249280208267255241147158186218134155285
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us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet ▃▇▆▄▄██▁▅▅▆▆▄▆▅▆▄▆▅▃▅▅▆▅▅-1418942-58-74137162-263-38-316962-9233-2713-6929-3-125-508517-21NANANA-62NANANA19NANANA59NANANA4NANANA117
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us-gaap:NetCashProvidedByUsedInInvestingActivities ▁▃▃▂▃▃▃▂▄▄▆█▃▁▂▃▂▃▃▂▃▂▂▃▄-4382-9-195-27-53-95-1673462651033147613-583-287115-1994815-2032-283-316-102156NANANA-62NANANA222NANANA-257NANANA-323NANANA-636
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us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▅▄▅▃▄▅▆▆▃▄▂▃▁▆▃▄▄▅██▅▇▅▅▄59586149576168664558434834694952526583806277646055NANANA60NANANA71NANANA56NANANA33NANANA21
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us-gaap:NetCashProvidedByUsedInFinancingActivities █▅▄▇▇▆▆▇▅▅▄▁▇▆▆▅█▃▅▇▇▆▇▇▆82-525-736-92-140-444-457-135-663-617-878-1512-258-271-371-640-4-979-582-33-95-430-254-189-260NANANA120NANANA-166NANANA34NANANA17NANANA13
 us-gaap:NetCashProvidedByUsedInFinancingActivities us-gaap:ConsolidationItems srt:ConsolidationEliminations█▁▁▁▂▅▃▁▂▅▁7105-313-25-9313238502086-4176574206-310NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:ProceedsFromIssuanceOfLongTermDebt ▆▄▅█▃▆▅▆▃▁▁▃▄▃▃▄▄▆▄▅▃▄▃▇▄2060113413592688871179414081744808306599927386731011104518571049157587098493121291195NANANA1150NANANA75NANANA429NANANA75NANANANA
 us-gaap:ProceedsFromIssuanceOfLongTermDebt us-gaap:ConsolidatedEntities aon:AonCorporation1603NANANA485NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ProceedsFromIssuanceOfLongTermDebt us-gaap:ConsolidatedEntities aon:AonUK457NANANA384NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:RepaymentsOfLongTermDebt ▅▄▆▆▃▇▆▅▃▁▁▄▄▃▃▆▂█▄▅▃▄▅▄▄13411083163015346941919147113237041810409506376761457175223896412106868451328916829NANANA715NANANA140NANANA79NANANANANANANANA
 us-gaap:RepaymentsOfLongTermDebt us-gaap:ConsolidatedEntities aon:AonCorporation1068NANANA310NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RepaymentsOfLongTermDebt us-gaap:ConsolidatedEntities aon:AonUK273NANANA384NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:RepaymentsOfLongTermDebt ▅▄▆▆▃▇▆▅▃▁▁▄▄▃▃▆▂█▄▅▃▄▅▄▄13411083163015346941919147113237041810409506376761457175223896412106868451328916829NANANA715NANANA140NANANA79NANANANANANANANA
 us-gaap:RepaymentsOfLongTermDebt us-gaap:ConsolidatedEntities aon:AonCorporation1068NANANA310NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RepaymentsOfLongTermDebt us-gaap:ConsolidatedEntities aon:AonUK273NANANA384NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A2.20SeniorNotesdueNovember20200.022NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A2.875notesdue20260.02875NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A3.50NotesdueJune20240.035NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A3.75SeniorNotesDueMay220290.0375NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A4.00SeniorNotesDueNovember20230.04NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A4.50SeniorNotesDueDecember20280.045NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A4.60SeniorNotesDueJune20440.046NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A5.00SeniorNotesDueSeptember20200.05NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:A8.205NotesDueJanuary20270.08205NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument aon:SeniorNotes625PercentDue20400.0625NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument,us-gaap:LongtermDebtType aon:A2.20SeniorNotesdueNovember2022,us-gaap:SeniorNotesNA0.022NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument,us-gaap:LongtermDebtType aon:A2.80SeniorNotesDueMarch2021,us-gaap:SeniorNotes0.028NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument,us-gaap:LongtermDebtType aon:A4.00SeniorNotesDueNovember2023,us-gaap:SeniorNotesNA0.04NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:DebtInstrument,us-gaap:LongtermDebtType aon:A4.60SeniorNotesDueJune2044,us-gaap:SeniorNotesNA0.046NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:LongtermDebtType aon:A3.75SeniorNotesDueMay22029NA0.0375NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:LongtermDebtType aon:A4.00SeniorNotesDueNovember2023NA0.04NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:LongtermDebtType aon:A4.60SeniorNotesDueJune2044NA0.046NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:LongtermDebtType aon:A5.00SeniorNotesDueSeptember2020NA0.05NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA

Common Stock Value

us-gaap:CommonStockValue



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
Value22222222223333333333333333333333386386386386386386363363363363362
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.01.31.31.31.31.31.31.61.51.61.61.6

Common Stock Par Or Stated Value Per Share

us-gaap:CommonStockParOrStatedValuePerShare



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-04-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value0.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.011.01.01.01.01.01.01.01.01.01.01.0
Percentage of CommonStockParOrStatedValuePerShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Shares Issued

Common Stock Shares Issued

us-gaap:CommonStockSharesIssued



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
Value234232234235240240241243245247250255262262263265264269273279281280285290296300301307301310318322386386386386386385362362362362361
Percentage of CommonStockSharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStockIncludingAdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-312009-12-312008-12-31
Value231232234235240240241243245247250255262262263265264269273279281280285290296300301307309310318322386386385362361
Percentage of CommonStockSharesIssued98.7100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0102.4100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Outstanding

Common Stock Shares Authorized

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value234239242243245247250257262267269269273283286287296301307312317320331335336336342345282282283292292292
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value233236240242244246248255262264267268271280284284292298303309313316327332332332337339278278275283285284
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value3.311.590.941.152.721.420.60.22.39-0.080.722.931.11.71.151.011.162.09999999999999961.050.631.151.61.061.021.070.830.770.820.950.620.740.720.850.590.760.720.680.520.550.650.710.420.520.99
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value3.291.580.931.142.71.410.60.192.37-0.070.722.931.091.681.141.011.152.081.040.621.141.561.041.011.060.820.760.820.930.620.730.710.830.590.750.710.670.510.540.630.690.410.510.96
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Income Loss From Continuing Operations Per Basic Share

us-gaap:IncomeLossFromContinuingOperationsPerBasicShare



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value3.311.590.941.152.721.140.610.192.370.040.74-0.20.951.71.191.121.22.121.050.631.151.61.061.021.071.160.830.770.820.950.620.740.720.840.590.760.720.680.520.640.650.510.410.520.81
Percentage of IncomeLossFromContinuingOperationsPerBasicShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Income Loss From Continuing Operations Per Diluted Share

us-gaap:IncomeLossFromContinuingOperationsPerDilutedShare



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value3.291.580.931.142.71.130.610.192.350.040.73-0.20.941.681.181.111.192.091.050.621.141.561.041.011.061.140.820.760.820.930.620.730.710.820.590.750.710.670.510.630.630.490.40.50.79
Percentage of IncomeLossFromContinuingOperationsPerDilutedShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Revenues

us-gaap:Revenues



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value321928852379260631432770234925613090290923402368238132622746276627923288274228052847329928802919294732092794289729153115273728212841299427232811275929091801189819042073179418821846
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



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
Value321928852379260631432770234925613090290923402368
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues srt:NonGuarantorSubsidiaries100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value-5-3-3-5-11-1-2-5-1-5-40-9-10-12-10-11-11-7-18
Percentage of Revenues-0.2-0.1-0.1-0.2-0.4-0.0-0.1-0.2-0.0-0.2-0.20.0-0.3-0.4-0.4-0.4-0.3-0.4-0.2-0.6
Percentage of Revenues-0.2-0.1-0.1-0.2-0.4-0.0-0.1-0.2-0.0-0.2-0.20.0-0.3-0.4-0.4-0.4-0.3-0.4-0.2-0.6
Percentage of Revenues us-gaap:IntersegmentElimination100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems, us-gaap:ProductOrService

us-gaap:OperatingSegments, aon:DataSolutions



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value3974844194201105501431424-126491389386-216466405395
Percentage of Revenues12.320.316.113.439.921.316.813.7-4.321.016.416.2-6.617.014.614.1
Percentage of Revenues12.320.316.113.439.921.316.813.7-4.321.016.416.2-6.617.014.614.1
Percentage of Revenues us-gaap:OperatingSegments aon:DataSolutions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, aon:Health



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value5022793174861596278309451538293312372532265281292
Percentage of Revenues15.611.712.215.557.611.812.114.618.512.513.215.616.39.710.210.5
Percentage of Revenues15.611.712.215.557.611.812.114.618.512.513.215.616.39.710.210.5
Percentage of Revenues us-gaap:OperatingSegments aon:Health100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, aon:PCAdvisory



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value11461057116711184652102911661184122691710429841094884990961
Percentage of Revenues35.644.444.835.6167.943.845.538.342.139.244.041.333.532.235.834.4
Percentage of Revenues35.644.444.835.6167.943.845.538.342.139.244.041.333.532.235.834.4
Percentage of Revenues us-gaap:OperatingSegments aon:PCAdvisory100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, aon:Reinsurance



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value8482914207881563279380742359355344371329329332371
Percentage of Revenues26.312.216.125.156.411.914.824.012.315.214.515.610.112.012.013.3
Percentage of Revenues26.312.216.125.156.411.914.824.012.315.214.515.610.112.012.013.3
Percentage of Revenues us-gaap:OperatingSegments aon:Reinsurance100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, aon:Retirement



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value3312712863361865263277294913289285268913260275259
Percentage of Revenues10.311.411.010.767.311.210.89.531.412.412.011.328.09.59.99.3
Percentage of Revenues10.311.411.010.767.311.210.89.531.412.412.011.328.09.59.99.3
Percentage of Revenues us-gaap:OperatingSegments aon:Retirement100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementGeographical

aon:AmericasOtherthanUnitedStates



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value228196256241226257203243237
Percentage of Revenues7.16.810.89.27.29.38.69.57.7
Percentage of Revenues7.16.810.89.27.29.38.69.57.7
Percentage of Revenues aon:AmericasOtherthanUnitedStates100.0100.0100.0100.0100.0100.0100.0100.0100.0

aon:EuropeMiddleEastAndAfrica



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312010-09-302010-06-302009-09-302009-06-30
Value9782835011009399493979393412409438
Percentage of Revenues30.411.919.232.117.019.331.721.821.722.823.3
Percentage of Revenues30.411.919.232.117.019.331.721.821.722.823.3
Percentage of Revenues aon:EuropeMiddleEastAndAfrica100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

country:GB



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value500292358400452394264413484
Percentage of Revenues15.510.115.015.314.414.211.216.115.7
Percentage of Revenues15.510.115.015.314.414.211.216.115.7
Percentage of Revenues country:GB100.0100.0100.0100.0100.0100.0100.0100.0100.0

country:US



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value122715001209114611611221121511251116
Percentage of Revenues38.152.050.844.036.944.151.743.936.1
Percentage of Revenues38.152.050.844.036.944.151.743.936.1
Percentage of Revenues country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0

srt:AsiaPacific



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value286273318295268287274
Percentage of Revenues8.911.512.29.411.411.28.9
Percentage of Revenues8.911.512.29.411.411.28.9
Percentage of Revenues srt:AsiaPacific100.0100.0100.0100.0100.0100.0100.0

Revenue From Contract With Customer Excluding Assessed Tax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value3219288523792606314310770234925613090290923402368238132622746276627923288274228052847329928802919294732092794289729153115273728212841299427232811275929091801189819042073179418821846
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues100.0100.0100.0100.0100.0388.8100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Costs And Expenses

us-gaap:CostsAndExpenses



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value2186236120192193227122712087257722912420207524862038269423242361234225712329252824062664246324742478243025152505239824272439238223772363153816301631160016621480
Percentage of CostsAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues67.981.884.984.272.382.088.8100.674.183.288.7105.085.682.684.685.483.978.284.990.184.580.885.584.884.187.086.885.987.686.085.987.584.685.685.485.985.789.288.380.2

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-613
Percentage of CostsAndExpenses-0.30.6
Percentage of Revenues-0.20.4
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value3820
Percentage of CostsAndExpenses1.70.9
Percentage of Revenues1.20.6
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value137198-13-4791-119-3
Percentage of CostsAndExpenses0.60.30.90.4-0.6-0.23.10.0-0.00.9-0.1
Percentage of Revenues0.50.30.70.3-0.5-0.23.10.0-0.00.8-0.1
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value215423481998214922432256207824812270224220392486
Percentage of CostsAndExpenses98.599.499.098.098.899.399.696.399.192.698.3100.0
Percentage of Revenues66.981.484.082.571.481.488.596.973.577.187.1105.0
Percentage of Revenues srt:NonGuarantorSubsidiaries66.981.484.082.571.481.488.596.973.577.187.1105.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value014252028131720672612
Percentage of CostsAndExpenses0.00.71.10.91.20.60.70.92.81.30.5
Percentage of Revenues0.00.61.00.61.00.60.70.62.31.10.5
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

Operating Income Loss

us-gaap:OperatingIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value1033524360413872499262-16799489265-118343568422405450717413277441635417445469515364382410461339394402435341434396422263268273241194220366
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues32.118.215.115.827.718.011.2-0.625.916.811.3-5.014.417.415.414.616.121.815.19.915.519.214.515.215.916.013.013.214.114.812.414.014.114.512.515.414.414.514.614.114.311.610.811.719.8

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value6-13
Percentage of OperatingIncomeLoss0.6-1.5
Percentage of Revenues0.2-0.4
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value-38-20
Percentage of OperatingIncomeLoss-3.7-2.3
Percentage of Revenues-1.2-0.6
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-13-7-19-8134-79-11-193
Percentage of OperatingIncomeLoss-2.5-1.9-4.6-0.92.61.5493.8-0.10.2-7.2-2.5
Percentage of Revenues-0.5-0.3-0.7-0.30.50.2-3.1-0.00.0-0.80.1
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value106553738145790051427180820667301-118
Percentage of OperatingIncomeLoss103.1102.5105.8110.7103.2103.0103.4-500.0102.6136.4113.6100.0
Percentage of Revenues33.118.616.017.528.618.611.53.126.522.912.9-5.0
Percentage of Revenues srt:NonGuarantorSubsidiaries33.118.616.017.528.618.611.53.126.522.912.9-5.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value0-14-25-20-28-13-17-20-67-26-12
Percentage of OperatingIncomeLoss0.0-3.9-6.1-2.3-5.6-5.0106.2-2.5-13.7-9.810.2
Percentage of Revenues0.0-0.6-1.0-0.6-1.0-0.6-0.7-0.6-2.3-1.1-0.5
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

Interest Expense

us-gaap:InterestExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value83807877727069697071707170707073696872686567656558534852575759606363503334322629
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues2.62.83.33.02.32.52.92.72.32.43.03.02.92.12.52.62.52.12.62.42.32.02.32.22.01.91.71.82.12.02.12.22.22.32.81.71.81.81.41.6

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value3928
Percentage of InterestExpense47.038.9
Percentage of Revenues1.20.9
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value1124
Percentage of InterestExpense13.333.3
Percentage of Revenues0.30.8
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value5446
Percentage of InterestExpense65.163.9
Percentage of Revenues1.71.5
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value3635342826262524232423
Percentage of InterestExpense45.044.944.238.937.137.736.234.332.434.332.4
Percentage of Revenues1.21.51.30.90.91.11.00.80.81.01.0
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value1066546107417
Percentage of InterestExpense1.20.07.77.86.95.78.714.510.05.61.49.9
Percentage of Revenues0.00.00.30.20.20.10.30.40.20.10.00.3
Percentage of Revenues srt:NonGuarantorSubsidiaries0.00.00.30.20.20.10.30.40.20.10.00.3

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value5047454654524849585346
Percentage of InterestExpense62.560.358.463.977.175.469.670.081.775.764.8
Percentage of Revenues1.72.01.71.51.92.21.91.62.02.31.9
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-22-6-10-8-7-14-15-14-10-14-8-5
Percentage of InterestExpense-26.5-7.5-12.8-10.4-9.7-20.0-21.7-20.3-14.3-19.7-11.4-7.0
Percentage of Revenues-0.7-0.2-0.4-0.3-0.2-0.5-0.6-0.5-0.3-0.5-0.3-0.2
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.00.0

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value292601-3-1520-5-5-10-279018-5281421035-213969-91207-2317-9571314-1
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.90.10.20.00.0-0.1-0.50.7-0.2-0.2-0.4-0.80.30.00.6-1.60.30.01.50.31.2-0.10.01.40.20.3-0.30.40.00.3-0.80.6-0.50.30.40.70.7-0.1

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-42-11
Percentage of OtherNonoperatingIncomeExpense-144.80.0
Percentage of Revenues-1.3-0.3
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value05
Percentage of OtherNonoperatingIncomeExpense0.00.0
Percentage of Revenues0.00.2
Percentage of Revenues aon:AonUK0.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value72724871913-612
Percentage of OtherNonoperatingIncomeExpense248.3350.0400.00.0700.0-633.3-86.7120.0-240.0
Percentage of Revenues2.20.30.90.30.30.70.4-0.30.5
Percentage of Revenues srt:NonGuarantorSubsidiaries2.20.30.90.30.30.70.4-0.30.5

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value-1-227-22-183010
Percentage of OtherNonoperatingIncomeExpense-3.4-1100.0116.70.0200.0600.0-20.0-0.0-200.0
Percentage of Revenues-0.0-0.90.3-0.10.1-0.70.10.00.4
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.0

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-397196-212-103133-181-50-460247-4424344147-268-89-59-79-66-229175-322-279-3187416155-58-174164-197104
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 Revenues-12.36.8-8.9-4.04.2-6.5-2.1-18.08.0-1.510.41.96.2-8.2-3.2-2.1-2.8-2.0-8.46.2-11.3-8.5-11.02.50.55.5-2.0-6.06.0-7.03.7

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



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-398205-234-96131-189-48-478250-4424354
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax100.3104.6110.493.298.5104.496.0103.9101.2100.0100.0122.7
Percentage of Revenues-12.47.1-9.8-3.74.2-6.8-2.0-18.78.1-1.510.42.3
Percentage of Revenues srt:NonGuarantorSubsidiaries-12.47.1-9.8-3.74.2-6.8-2.0-18.78.1-1.510.42.3

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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
Value1-922-728-218-300-10
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax-0.3-4.6-10.46.81.5-4.44.0-3.9-1.2-0.00.0-22.7
Percentage of Revenues0.0-0.30.9-0.30.10.3-0.10.7-0.10.00.0-0.4
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312013-03-31
Value-395-208-103131-183-47-454244-4623649146-174
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax99.598.1100.098.5101.194.098.798.8104.597.1111.499.3100.0
Percentage of Revenues-12.3-8.7-4.04.2-6.6-2.0-17.77.9-1.610.12.16.1-6.0
Percentage of Revenues us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NoncontrollingInterest



Period End2020-03-312019-09-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-2-422-3-6327-51
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax0.51.91.5-1.16.01.31.2-4.52.9-11.40.7
Percentage of Revenues-0.1-0.20.10.1-0.1-0.20.10.10.3-0.20.0
Percentage of Revenues us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value7923822292876762841555760417196-43265384314280327590303188341467315313336264252272307210255249280208265253242147184186162131153235
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues24.613.29.611.021.510.36.62.219.50.68.4-1.811.111.811.410.111.717.911.16.712.014.210.910.711.49.48.79.39.97.79.08.89.47.69.49.28.38.29.79.87.87.38.112.7

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-258-211
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest-32.6-31.2
Percentage of Revenues-8.0-6.7
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-9-19
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest-1.1-2.8
Percentage of Revenues-0.3-0.6
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value14-21
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest1.8-3.1
Percentage of Revenues0.4-0.7
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-217-143-274-211-239-322-191-123-363-338-104
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest-56.8-62.4-95.5-31.2-84.2-207.7-335.1-20.4-2135.3-172.4241.9
Percentage of Revenues-7.5-6.0-10.5-6.7-8.6-13.7-7.5-4.0-12.5-14.4-4.4
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value1046553480495910587288370851432313162
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest132.1144.8209.6172.5134.6206.7185.8649.1140.92541.2159.7-376.7
Percentage of Revenues32.519.220.219.029.021.212.314.427.514.913.46.8
Percentage of Revenues srt:NonGuarantorSubsidiaries32.519.220.219.029.021.212.314.427.514.913.46.8

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value37-8659-21-56187-104-127-52221-111
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest9.7-37.620.6-3.1-19.7120.6-182.5-21.0-305.9112.8258.1
Percentage of Revenues1.3-3.62.3-0.7-2.08.0-4.1-4.1-1.89.4-4.7
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-19-227-2-82-1830010
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest-0.12.4-9.62.4-0.3-2.81.3-31.60.50.00.0-23.3
Percentage of Revenues-0.00.3-0.90.3-0.1-0.30.1-0.70.10.00.00.4
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations Before Income Taxes Domestic

Income Loss From Continuing Operations Before Income Taxes Foreign

Nonoperating Income Expense

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value18959565612613739-1441143894-14306248557411249268011475677889909664969784871036160614757108
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues5.92.02.42.14.04.91.7-5.63.713.40.2-6.00.01.91.72.02.73.41.80.92.83.52.62.32.63.23.13.32.33.43.43.13.13.73.43.23.22.63.05.9

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-48-42
Percentage of IncomeTaxExpenseBenefit-25.4-33.3
Percentage of Revenues-1.5-1.3
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-2-5
Percentage of IncomeTaxExpenseBenefit-1.1-4.0
Percentage of Revenues-0.1-0.2
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value-17-5
Percentage of IncomeTaxExpenseBenefit-9.0-4.0
Percentage of Revenues-0.5-0.2
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-41-35-64-42-48-67-50-2788-81-63
Percentage of IncomeTaxExpenseBenefit-69.5-62.5-114.3-33.3-35.0-171.834.7-23.722.6-2025.044.1
Percentage of Revenues-1.4-1.5-2.5-1.3-1.7-2.9-2.0-0.93.0-3.5-2.7
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value25610593120173218114-9115731493-72
Percentage of IncomeTaxExpenseBenefit135.4178.0166.1214.3137.3159.1292.363.2137.780.72325.050.3
Percentage of Revenues8.03.63.94.65.57.94.9-3.65.110.84.0-3.0
Percentage of Revenues srt:NonGuarantorSubsidiaries8.03.63.94.65.57.94.9-3.65.110.84.0-3.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-5-20-5-33-8-3-16-13-8-8
Percentage of IncomeTaxExpenseBenefit-8.5-3.60.0-4.0-24.1-20.52.1-14.0-3.3-200.05.6
Percentage of Revenues-0.2-0.10.0-0.2-1.2-0.3-0.1-0.5-0.4-0.3-0.3
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

Income Taxes Paid Net

us-gaap:IncomeTaxesPaidNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value537482164336367149583287465058656448416962724657761386614840361053
Percentage of IncomeTaxesPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues1.62.63.46.31.02.32.95.81.911.331.92.12.42.02.31.71.52.12.32.61.61.72.64.72.25.11.41.30.52.9

Profit Loss

us-gaap:ProfitLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value79138222828767635315358610-12192778305459314280327590303188341467315313336360264252272307210254249280208267255241147158186218134155285
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues24.613.29.611.021.512.76.52.319.7-0.48.232.912.814.111.410.111.717.911.16.712.014.210.910.711.411.29.48.79.39.97.79.08.89.47.69.59.28.38.28.39.810.57.58.215.4

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value604513
Percentage of ProfitLoss76.475.9
Percentage of Revenues18.816.3
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value605600
Percentage of ProfitLoss76.588.8
Percentage of Revenues18.819.1
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonIreland



Period End2020-03-312019-03-31
Value7730
Percentage of ProfitLoss97.70.0
Percentage of Revenues24.00.0
Percentage of Revenues aon:AonIreland0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value773661
Percentage of ProfitLoss97.797.8
Percentage of Revenues24.021.0
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-95-3627513-103-36415582-270-216531
Percentage of ProfitLoss-24.9-15.89.475.9-29.2-237.925.995.42250.0-112.568.3
Percentage of Revenues-3.3-1.51.016.3-3.7-15.50.618.8-9.3-9.222.4
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value10454584435221423553-783861439133931514
Percentage of ProfitLoss132.1119.9194.3181.9210.5156.7-51.0665.5235.9-1108.348.4194.6
Percentage of Revenues32.515.918.620.045.320.0-3.315.146.64.64.063.9
Percentage of Revenues srt:NonGuarantorSubsidiaries32.515.918.620.045.320.0-3.315.146.64.64.063.9

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value36524427066135314566591-19185759
Percentage of ProfitLoss95.5107.094.197.8100.094.8113.896.9158.396.497.6
Percentage of Revenues12.710.310.421.012.76.22.619.1-0.77.932.1
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-3009-346-423-532-1921-450450-409-2002144130-2026
Percentage of ProfitLoss-380.4-90.6-185.5-185.4-284.2-127.5294.1-705.2-328.2-1200.067.7-260.4
Percentage of Revenues-93.5-12.0-17.8-20.4-61.1-16.219.2-16.0-64.85.05.6-85.6
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest



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
Value1961017861016779147781268101386911111198
Percentage of ProfitLoss2.42.63.52.52.33.917.22.6-58.33.61.24.61.52.22.93.71.02.65.33.81.71.92.93.34.04.43.54.3
Percentage of Revenues0.60.30.40.50.30.30.40.50.20.30.40.60.20.30.30.40.20.30.40.50.20.20.30.40.40.40.30.4
Percentage of Revenues us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



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
Value77222227765934514748594-19185769291502307272315584295178328459309304325261238246178
Percentage of ProfitLoss97.697.496.597.597.796.182.897.4158.396.498.895.4109.497.897.196.399.097.494.796.298.398.197.196.796.095.696.595.7
Percentage of Revenues24.09.310.621.012.56.31.919.2-0.77.932.512.215.411.29.811.317.810.86.311.513.910.710.411.09.08.48.99.3
Percentage of Revenues us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-30
Value396371291808286839-285900-103450842453383236260286147836935-15794063794272099638653369-2021620336463-152202412
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues12.312.91.26.926.32.51.7-11.129.1-3.519.235.619.011.78.69.41.018.72.813.21.2-4.80.313.912.915.37.23.314.11.913.0-7.40.67.420.23.3-8.011.321.9

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value234652
Percentage of ComprehensiveIncomeNetOfTax59.178.7
Percentage of Revenues7.320.7
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value235739
Percentage of ComprehensiveIncomeNetOfTax59.389.3
Percentage of Revenues7.323.5
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonIreland



Period End2020-03-312019-03-31
Value3960
Percentage of ComprehensiveIncomeNetOfTax100.00.0
Percentage of Revenues12.30.0
Percentage of Revenues aon:AonIreland0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value396828
Percentage of ComprehensiveIncomeNetOfTax100.0100.0
Percentage of Revenues12.326.3
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-88-246-81652-357-488-323881-35939612
Percentage of ComprehensiveIncomeNetOfTax-23.7-848.3-45.078.7-525.0-1251.3113.397.9348.58.772.7
Percentage of Revenues-3.1-10.3-3.120.7-12.9-20.8-12.628.5-12.31.725.8
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value6385482304168839-324-3202017775961659
Percentage of ComprehensiveIncomeNetOfTax161.1147.76.9168.9203.957.4-830.8112.3224.1-74.8132.4197.0
Percentage of Revenues19.819.00.111.753.71.4-13.8-12.565.32.625.570.1
Percentage of Revenues srt:NonGuarantorSubsidiaries19.819.00.111.753.71.4-13.8-12.565.32.625.570.1

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value371291808286839-285900-103450842
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues12.91.26.926.32.51.7-11.129.1-3.519.235.6
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-1503-460244-223-2340318812643-2898282-635-2271
Percentage of ComprehensiveIncomeNetOfTax-379.5-124.0841.4-123.9-282.6467.62082.1-225.6-322.0-273.8-141.1-269.7
Percentage of Revenues-46.7-15.910.3-8.6-74.511.534.625.1-93.89.7-27.1-95.9
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

Net Income Loss

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value77237422227765934514748594-19185769291452307272315584295178328459309304325355256241261305204246238277198258246231144153178
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues24.013.09.310.621.012.56.31.919.2-0.77.932.512.213.911.29.811.317.810.86.311.513.910.710.411.011.19.28.39.09.87.58.78.49.37.39.28.97.98.08.19.3

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value604513
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic78.277.8
Percentage of Revenues18.816.3
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value605600
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic78.491.0
Percentage of Revenues18.819.1
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonIreland



Period End2020-03-312019-03-31
Value7730
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.10.0
Percentage of Revenues24.00.0
Percentage of Revenues aon:AonIreland0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value773661
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.1100.3
Percentage of Revenues24.021.0
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-95-3627513-103-36415582-270-216531
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic-25.4-16.29.777.8-29.9-247.631.298.01421.1-116.869.1
Percentage of Revenues-3.3-1.51.016.3-3.7-15.50.618.8-9.3-9.222.4
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value10264504375121406545-843761423126861505
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic132.9120.3196.8184.8213.4158.0-57.1783.3239.6-663.246.5195.7
Percentage of Revenues31.915.618.419.644.719.7-3.614.746.14.33.763.6
Percentage of Revenues srt:NonGuarantorSubsidiaries31.915.618.419.644.719.7-3.614.746.14.33.763.6

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value36524427066135314566591-19185759
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic97.6109.997.5100.3102.398.6137.599.5100.0100.098.7
Percentage of Revenues12.710.310.421.012.76.22.619.1-0.77.932.1
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-3009-346-423-532-1921-450450-409-2002144130-2026
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic-389.8-92.5-190.5-192.1-291.5-130.4306.1-852.1-337.0-757.970.3-263.5
Percentage of Revenues-93.5-12.0-17.8-20.4-61.1-16.219.2-16.0-64.85.05.6-85.6
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value19861017861016779147781268101386911581111268113109910358201465
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.60.30.30.40.50.30.30.40.50.20.30.40.60.20.30.30.40.20.30.40.50.20.20.30.40.20.30.40.40.10.20.30.40.10.40.30.30.30.20.30.41.00.80.30.3

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



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
Value19861017861016779
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.60.30.30.40.50.30.30.40.50.20.30.4
Percentage of Revenues srt:NonGuarantorSubsidiaries0.60.30.30.40.50.30.30.40.50.20.30.4

Assets

us-gaap:Assets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value30282294052816729807291352642225602272172784726088259242718926982266152525226693268132716427206292032838929772288273177630077302512930530062300293048629509308073027129552287453049629802289822335823956229592295822940
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value2392323977
Percentage of Assets79.081.5
Percentage of Assets79.081.5
Percentage of Assets aon:AonCorporation100.0100.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value900112304
Percentage of Assets29.741.8
Percentage of Assets29.741.8
Percentage of Assets aon:AonGlobalHoldingsLimited100.0100.0

aon:AonIreland



Period End2020-03-312019-12-31
Value31693375
Percentage of Assets10.511.5
Percentage of Assets10.511.5
Percentage of Assets aon:AonIreland100.0100.0

aon:AonUK



Period End2020-03-312019-12-31
Value934410102
Percentage of Assets30.934.4
Percentage of Assets30.934.4
Percentage of Assets aon:AonUK100.0100.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value2397726697259782389821659257442604522563
Percentage of Assets81.594.887.282.082.0100.695.786.5
Percentage of Assets81.594.887.282.082.0100.695.786.5
Percentage of Assets srt:GuarantorSubsidiaries100.0100.0100.0100.0100.0100.0100.0100.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value525254731147517486524745443778451474759244525
Percentage of Assets173.5160.9168.7163.2162.9165.7176.3174.9170.7
Percentage of Assets173.5160.9168.7163.2162.9165.7176.3174.9170.7
Percentage of Assets srt:NonGuarantorSubsidiaries100.0100.0100.0100.0100.0100.0100.0100.0100.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value10102969496029945912210763109159565
Percentage of Assets34.434.432.234.134.542.040.136.7
Percentage of Assets34.434.432.234.134.542.040.136.7
Percentage of Assets srt:ParentCompany100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-67680-51985-55741-54425-52162-48137-56052-57335-50565
Percentage of Assets-223.5-176.8-197.9-182.6-179.0-182.2-218.9-210.7-193.8
Percentage of Assets-223.5-176.8-197.9-182.6-179.0-182.2-218.9-210.7-193.8
Percentage of Assets srt:ConsolidationEliminations100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities



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
Value27022259562460625894242732220321274225992246221440206772163621156210831975821132214662100121264227472195823141215552401722071220562171522444223962268121148225972185521432204662203121315206761751418478175021752717525
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets89.288.387.486.983.384.083.183.080.782.279.879.678.479.278.279.280.177.378.277.977.377.774.875.673.472.974.174.774.674.471.773.472.272.571.272.271.571.375.077.176.276.376.4

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value2874124934
Percentage of Liabilities106.496.1
Percentage of Assets94.984.8
Percentage of Assets aon:AonCorporation120.1104.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value612055
Percentage of Liabilities0.27.9
Percentage of Assets0.27.0
Percentage of Assets aon:AonGlobalHoldingsLimited0.716.7

aon:AonUK



Period End2020-03-312019-12-31
Value61756727
Percentage of Liabilities22.925.9
Percentage of Assets20.422.9
Percentage of Assets aon:AonUK66.166.6

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value2493427422264022425322556261152511922544
Percentage of Liabilities96.1111.4102.099.9101.6122.8111.2105.1
Percentage of Assets84.897.488.683.285.4102.092.386.4
Percentage of Assets srt:GuarantorSubsidiaries104.0102.7101.6101.5104.1101.496.499.9

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value190621886818311194911816516212161371827617667
Percentage of Liabilities70.572.774.475.374.873.075.980.982.4
Percentage of Assets62.964.265.065.462.361.463.067.167.7
Percentage of Assets srt:NonGuarantorSubsidiaries36.339.938.540.138.337.035.738.439.7

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value67276202576651704971650163704982
Percentage of Liabilities25.925.222.321.322.430.628.223.2
Percentage of Assets22.922.019.317.718.825.423.419.1
Percentage of Assets srt:ParentCompany66.664.060.052.054.560.458.452.1

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-27017-24573-27329-25765-23315-21536-27479-27166-23753
Percentage of Liabilities-100.0-94.7-111.1-99.5-96.1-97.0-129.2-120.2-110.8
Percentage of Assets-89.2-83.6-97.0-86.4-80.0-81.5-107.3-99.8-91.0
Percentage of Assets srt:ConsolidationEliminations39.947.349.047.344.744.749.047.447.0

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value30282294052816729807291352642225602272172784726088259242718926982266152525226693268132716427206292032838929772288273177630077302512930530062300293048629509308073027129552287453049629802289822335823956229592295822940
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value2392323977
Percentage of LiabilitiesAndStockholdersEquity79.081.5
Percentage of Assets79.081.5
Percentage of Assets aon:AonCorporation100.0100.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value900112304
Percentage of LiabilitiesAndStockholdersEquity29.741.8
Percentage of Assets29.741.8
Percentage of Assets aon:AonGlobalHoldingsLimited100.0100.0

aon:AonIreland



Period End2020-03-312019-12-31
Value31693375
Percentage of LiabilitiesAndStockholdersEquity10.511.5
Percentage of Assets10.511.5
Percentage of Assets aon:AonIreland100.0100.0

aon:AonUK



Period End2020-03-312019-12-31
Value934410102
Percentage of LiabilitiesAndStockholdersEquity30.934.4
Percentage of Assets30.934.4
Percentage of Assets aon:AonUK100.0100.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value2397726697259782389821659257442604522563
Percentage of LiabilitiesAndStockholdersEquity81.594.887.282.082.0100.695.786.5
Percentage of Assets81.594.887.282.082.0100.695.786.5
Percentage of Assets srt:GuarantorSubsidiaries100.0100.0100.0100.0100.0100.0100.0100.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value525254731147517486524745443778451474759244525
Percentage of LiabilitiesAndStockholdersEquity173.5160.9168.7163.2162.9165.7176.3174.9170.7
Percentage of Assets173.5160.9168.7163.2162.9165.7176.3174.9170.7
Percentage of Assets srt:NonGuarantorSubsidiaries100.0100.0100.0100.0100.0100.0100.0100.0100.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value10102969496029945912210763109159565
Percentage of LiabilitiesAndStockholdersEquity34.434.432.234.134.542.040.136.7
Percentage of Assets34.434.432.234.134.542.040.136.7
Percentage of Assets srt:ParentCompany100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-67680-51985-55741-54425-52162-48137-56052-57335-50565
Percentage of LiabilitiesAndStockholdersEquity-223.5-176.8-197.9-182.6-179.0-182.2-218.9-210.7-193.8
Percentage of Assets-223.5-176.8-197.9-182.6-179.0-182.2-218.9-210.7-193.8
Percentage of Assets srt:ConsolidationEliminations100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity



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
Value3169337534923836477541514262454553014583517554875754547554345499528161065883639863656571721577007946814575347559757977628305815283588078823383988423825157925428540253795310
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets10.511.512.412.916.415.716.616.719.017.620.020.221.320.621.520.619.722.521.621.922.422.125.024.226.426.925.725.125.225.528.126.527.627.328.627.528.328.524.822.723.523.423.1

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value-4818-957
Percentage of StockholdersEquity-152.0-28.4
Percentage of Assets-15.9-3.3
Percentage of Assets aon:AonCorporation-20.1-4.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value894010249
Percentage of StockholdersEquity282.1303.7
Percentage of Assets29.534.9
Percentage of Assets aon:AonGlobalHoldingsLimited99.383.3

aon:AonIreland



Period End2020-03-312019-12-31
Value31693375
Percentage of StockholdersEquity100.0100.0
Percentage of Assets10.511.5
Percentage of Assets aon:AonIreland100.0100.0

aon:AonUK



Period End2020-03-312019-12-31
Value31693375
Percentage of StockholdersEquity100.0100.0
Percentage of Assets10.511.5
Percentage of Assets aon:AonUK33.933.4

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-957-725-424-355-897-37192619
Percentage of StockholdersEquity-28.4-20.8-11.1-7.4-21.6-8.720.40.4
Percentage of Assets-3.3-2.6-1.4-1.2-3.4-1.43.40.1
Percentage of Assets srt:GuarantorSubsidiaries-4.0-2.7-1.6-1.5-4.1-1.43.60.1

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value333722836929137290842920227498289442924326793
Percentage of StockholdersEquity1053.1840.6834.4758.2611.6662.4679.1643.4584.6
Percentage of Assets110.296.5103.497.6100.2104.1113.1107.4102.7
Percentage of Assets srt:NonGuarantorSubsidiaries63.560.061.359.861.562.864.161.460.2

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value33753492383647754151426245454583
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.512.412.916.415.716.616.717.6
Percentage of Assets srt:ParentCompany33.436.040.048.045.539.641.647.9

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-40663-27412-28412-28660-28847-26601-28573-30169-26812
Percentage of StockholdersEquity-1283.1-812.2-813.6-747.1-604.1-640.8-670.4-663.8-585.0
Percentage of Assets-134.3-93.2-100.9-96.2-99.0-100.7-111.6-110.8-102.8
Percentage of Assets srt:ConsolidationEliminations60.152.751.052.755.355.351.052.653.0

Assets Current

us-gaap:AssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value17345164761531716745159191437213348148601511513677142671560215393131461247113801140411397213920156551499915823147551771116173163301557416393162571638215702170561620715505145001593115211145191461215497142681398914526
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets57.356.054.456.254.654.452.154.654.352.455.057.457.049.449.451.752.451.451.253.652.853.151.255.753.854.053.154.554.153.753.255.453.552.550.452.251.050.162.664.762.160.963.3

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value29653520
Percentage of AssetsCurrent17.121.4
Percentage of Assets9.812.0
Percentage of Assets aon:AonCorporation12.414.7

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value12689
Percentage of AssetsCurrent0.70.5
Percentage of Assets0.40.3
Percentage of Assets aon:AonGlobalHoldingsLimited1.40.7

aon:AonUK



Period End2020-03-312019-12-31
Value208246
Percentage of AssetsCurrent1.21.5
Percentage of Assets0.70.8
Percentage of Assets aon:AonUK2.22.4

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value35205689492730801831616463323956
Percentage of AssetsCurrent21.437.129.419.312.746.242.628.9
Percentage of Assets12.020.216.510.66.924.123.315.2
Percentage of Assets srt:GuarantorSubsidiaries14.721.319.012.98.523.924.317.5

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value331672891828806294092797925673253752640724151
Percentage of AssetsCurrent191.2175.5188.1175.6175.8178.6190.1177.7176.6
Percentage of Assets109.598.3102.398.796.097.299.197.092.6
Percentage of Assets srt:NonGuarantorSubsidiaries63.161.160.660.459.058.656.255.554.2

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value246153167166191165171167
Percentage of AssetsCurrent1.51.01.01.01.31.21.21.2
Percentage of Assets0.80.50.60.60.70.60.60.6
Percentage of Assets srt:ParentCompany2.41.61.71.72.11.51.61.7

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-19121-16208-19331-17758-15306-13323-18356-18050-14597
Percentage of AssetsCurrent-110.2-98.4-126.2-106.0-96.1-92.7-137.5-121.5-106.7
Percentage of Assets-63.1-55.1-68.6-59.6-52.5-50.4-71.7-66.3-56.0
Percentage of Assets srt:ConsolidationEliminations28.331.234.732.629.327.732.731.528.9

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-312008-12-312007-12-312006-12-31
Value690790602581600656484487597756749684433431483438465384398367378374382418338477369266408291290286323272295300682346335260422217580537501582584281
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.32.72.11.92.12.51.91.82.12.92.92.51.61.61.91.61.71.41.51.31.31.31.31.31.11.61.30.91.41.01.00.91.10.91.01.02.31.21.41.11.80.90.00.00.02.50.00.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value1942271
Percentage of CashAndCashEquivalentsAtCarryingValue28.1287.5
Percentage of Assets0.67.7
Percentage of Assets aon:AonCorporation0.89.5

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value360
Percentage of CashAndCashEquivalentsAtCarryingValue5.20.0
Percentage of Assets0.10.0
Percentage of Assets aon:AonGlobalHoldingsLimited0.40.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value227115301371746862192729272524
Percentage of CashAndCashEquivalentsAtCarryingValue287.5254.2236.0124.3131.4398.1601.0333.9
Percentage of Assets7.75.44.62.63.37.510.89.7
Percentage of Assets srt:GuarantorSubsidiaries9.55.75.33.14.07.511.211.2

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value1698468491537563575400672793
Percentage of CashAndCashEquivalentsAtCarryingValue246.159.281.692.493.887.782.6138.0104.9
Percentage of Assets5.61.61.71.81.92.21.62.53.0
Percentage of Assets srt:NonGuarantorSubsidiaries3.21.01.01.11.21.30.91.41.8

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value0.00.00.00.00.00.00.01000000.0
Percentage of CashAndCashEquivalentsAtCarryingValue0.00.00.00.00.00.00.00.1
Percentage of Assets0.00.00.00.00.00.00.00.0
Percentage of Assets srt:ParentCompany0.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-1238-1949-1419-1327-709-781-1843-3112-2562
Percentage of CashAndCashEquivalentsAtCarryingValue-179.4-246.7-235.7-228.4-118.2-119.1-380.8-639.0-338.9
Percentage of Assets-4.1-6.6-5.0-4.5-2.4-3.0-7.2-11.4-9.8
Percentage of Assets srt:ConsolidationEliminations1.83.72.52.41.41.63.35.45.1

Short Term Investments

us-gaap:ShortTermInvestments



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
Value170138177235134172167173118529164027462002904632515873563854843433942173083405233573073523467185165107856075155897852114474312422684
Percentage of ShortTermInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.60.50.60.80.50.70.70.60.42.06.310.10.71.11.80.92.21.31.41.71.21.30.81.01.11.71.21.01.21.12.41.71.72.72.11.72.02.79.12.01.41.83.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value5728
Percentage of ShortTermInvestments33.520.3
Percentage of Assets0.20.1
Percentage of Assets aon:AonCorporation0.20.1

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value286312547564759355
Percentage of ShortTermInvestments20.335.653.235.132.628.134.167.1
Percentage of Assets0.10.20.40.20.20.20.21.4
Percentage of Assets srt:GuarantorSubsidiaries0.10.20.50.20.30.20.21.6

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value11311011411087116120114174
Percentage of ShortTermInvestments66.579.764.446.864.967.471.965.932.9
Percentage of Assets0.40.40.40.40.30.40.50.40.7
Percentage of Assets srt:NonGuarantorSubsidiaries0.20.20.20.20.20.30.30.20.4

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value35543112286632273242276026562992305327302478206821912103258923912516259127342453268426722815263028032880289626662838288431012959307531643183274527852650270120861994198320521990
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.710.610.210.811.110.410.411.011.00.09.58.08.17.89.79.59.49.710.19.09.29.49.59.18.89.69.69.19.49.610.210.010.010.510.89.59.18.99.38.98.38.68.98.7

us-gaap:ConsolidatedEntities

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value00000002
Percentage of AccountsReceivableNetCurrent0.00.00.00.00.00.00.00.1
Percentage of Assets0.00.00.00.00.00.00.00.0
Percentage of Assets srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value355431122866322732422760265629922476
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.099.9
Percentage of Assets11.710.610.210.811.110.410.411.09.5
Percentage of Assets srt:NonGuarantorSubsidiaries6.86.66.06.66.86.35.96.35.6

Other Assets Current

us-gaap:OtherAssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value5306026316315316187277326095872895183993093514243956225667287317126027111396577563484406389430392443415427538571681624532543462463355
Percentage of OtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.82.02.22.11.82.32.82.72.20.01.12.01.51.11.31.71.52.32.12.72.52.52.02.54.41.91.91.71.41.31.41.31.41.41.41.91.92.32.22.32.32.02.01.5

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value47
Percentage of OtherAssetsCurrent0.81.2
Percentage of Assets0.00.0
Percentage of Assets aon:AonCorporation0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value7610101615329
Percentage of OtherAssetsCurrent1.21.01.61.92.62.10.410.0
Percentage of Assets0.00.00.00.00.10.10.00.1
Percentage of Assets srt:GuarantorSubsidiaries0.00.00.00.00.10.10.00.1

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value526595625621521602712729259
Percentage of OtherAssetsCurrent99.298.899.098.498.197.497.999.689.6
Percentage of Assets1.72.02.22.11.82.32.82.71.0
Percentage of Assets srt:NonGuarantorSubsidiaries1.01.31.31.31.11.41.61.50.6

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value0.00.00.00.00.00.00.01000000.0
Percentage of OtherAssetsCurrent0.00.00.00.00.00.00.00.3
Percentage of Assets0.00.00.00.00.00.00.00.0
Percentage of Assets srt:ParentCompany0.00.00.00.00.00.00.00.0

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
Value17801733173323252381231122892189197118771489
Percentage of PropertyPlantAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.16.66.68.78.87.87.67.26.76.56.5

us-gaap:PropertyPlantAndEquipmentByType

aon:FurnitureFixturesAndEquipment



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value225228240300315313323331326342258
Percentage of PropertyPlantAndEquipmentGross12.613.213.812.913.213.514.115.116.518.217.3
Percentage of Assets0.80.90.91.11.21.11.11.11.11.21.1
Percentage of Assets aon:FurnitureFixturesAndEquipment0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ComputerEquipment



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value250279295417358347341332274245225
Percentage of PropertyPlantAndEquipmentGross14.016.117.017.915.015.014.915.213.913.115.1
Percentage of Assets0.91.11.11.61.31.21.11.10.90.81.0
Percentage of Assets us-gaap:ComputerEquipment0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ComputerSoftwareIntangibleAsset



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value72769368094810951020997867
Percentage of PropertyPlantAndEquipmentGross40.840.039.240.846.044.143.639.6
Percentage of Assets2.52.62.63.64.03.43.32.8
Percentage of Assets us-gaap:ComputerSoftwareIntangibleAsset0.00.00.00.00.00.00.00.0

us-gaap:ConstructionInProgress



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value183154799376947010987458
Percentage of PropertyPlantAndEquipmentGross10.38.94.64.03.24.13.15.04.42.40.5
Percentage of Assets0.60.60.30.30.30.30.20.40.30.20.0
Percentage of Assets us-gaap:ConstructionInProgress0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:LeaseholdImprovements



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value358334349452422413434426407436366
Percentage of PropertyPlantAndEquipmentGross20.119.320.119.417.717.919.019.520.623.224.6
Percentage of Assets1.21.31.31.71.61.41.41.41.41.51.6
Percentage of Assets us-gaap:LeaseholdImprovements0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:PropertyPlantAndEquipmentOtherTypes



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value374590115115124124124
Percentage of PropertyPlantAndEquipmentGross2.12.65.24.94.85.45.45.7
Percentage of Assets0.10.20.30.40.40.40.40.4
Percentage of Assets us-gaap:PropertyPlantAndEquipmentOtherTypes0.00.00.00.00.00.00.00.0

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value11591145116915601616154614981369118810961028
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.94.34.55.95.95.25.04.54.03.84.5

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value666621606599606588594575578564545556536765738751766765785782754765760787785791803808816820814797808783773798791781468450452461451
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.22.12.22.02.12.22.32.12.12.22.12.02.02.92.92.82.92.82.92.72.72.62.62.52.62.62.72.72.72.72.82.62.72.62.72.62.72.72.01.92.02.02.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value666621606599606588594575564
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.22.12.22.02.12.22.32.12.2
Percentage of Assets srt:NonGuarantorSubsidiaries1.31.31.31.21.31.31.31.21.3

Long Term Investments

us-gaap:LongTermInvestments



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
Value5253525455545254585744122121119124127131135136142143143143138143132139172152165160200211239254249318312301301308319332
Percentage of LongTermInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.20.20.20.20.20.20.20.20.20.20.20.40.40.40.50.50.50.50.50.50.50.50.50.40.50.40.50.60.50.50.50.60.70.80.90.81.11.11.31.31.31.41.4

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
Value8293816580718198821981718282829185508358788877457544874784528473841184488571866185488860902690999030899789588795878689438856871388968770883589758895864759765710588760785637
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 Assets27.427.828.727.528.230.932.330.530.732.030.428.528.032.933.531.731.431.131.529.730.129.831.328.630.029.730.629.329.329.330.028.329.429.730.729.429.829.825.623.825.626.524.6

us-gaap:BusinessAcquisition

aon:A2018And2019Acquisitions



Period End2019-12-31
Value34
Percentage of Goodwill0.4
Percentage of Assets0.1
Percentage of Assets aon:A2018And2019Acquisitions0.0

aon:A2019And2020Acquisitions



Period End2020-03-31
Value303
Percentage of Goodwill3.7
Percentage of Assets1.0
Percentage of Assets aon:A2019And2020Acquisitions0.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value829381658071819882198171828282918358
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets27.427.828.727.528.230.932.330.532.0
Percentage of Assets srt:NonGuarantorSubsidiaries15.817.317.016.917.318.718.317.418.8

Intangible Assets Net Excluding Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill



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
Value7467838749731077114912601363166217331341140218862223203821072108218022572350241025202612246825002578265727362844297530403106320332763361348435473611754753770791779
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.52.73.13.33.74.34.95.06.06.65.25.27.08.48.17.97.98.08.38.08.58.59.17.88.38.59.19.19.59.810.310.110.611.111.711.411.912.53.23.13.43.43.4

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value74678387497310771149126013631733
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.52.73.13.33.74.34.95.06.6
Percentage of Assets srt:NonGuarantorSubsidiaries1.41.71.82.02.32.62.82.93.9

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

aon:CustomerRelatedAndContractBased



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-31
Value63766469873778179684889311191135724743816113796810241020107711461224127813731452131913431410146815351633174517971853193119932261
Percentage of IntangibleAssetsNetExcludingGoodwill85.484.879.975.772.569.367.365.567.365.554.053.043.351.147.548.648.449.450.852.153.054.555.653.453.754.755.356.157.458.759.159.760.360.862.6
Percentage of Assets2.12.32.52.52.73.03.33.34.04.42.82.73.04.33.83.83.84.04.24.24.54.65.04.24.54.75.05.15.45.76.16.06.46.77.8
Percentage of Assets aon:CustomerRelatedAndContractBased0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

aon:MarketingTechnologyAndOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-31
Value88465055616669738084544571885164698492107113128141130138149164176186201215227245256323
Percentage of IntangibleAssetsNetExcludingGoodwill11.85.95.75.75.75.75.55.44.84.84.03.23.84.02.53.03.33.94.14.64.75.15.45.35.55.86.26.46.56.87.17.37.67.88.9
Percentage of Assets0.30.20.20.20.20.20.30.30.30.30.20.20.30.30.20.20.30.30.30.40.40.40.50.40.50.50.60.60.60.70.70.70.80.91.1
Percentage of Assets aon:MarketingTechnologyAndOther0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TradeNames



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value217312618123528734339746351456361499810191019101943
Percentage of IntangibleAssetsNetExcludingGoodwill2.89.314.418.621.825.027.229.127.929.742.043.844.946.740.439.50.10.1
Percentage of Assets0.10.20.40.60.81.11.31.51.72.02.22.33.73.83.43.40.00.0
Percentage of Assets us-gaap:TradeNames0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Finite Lived Intangible Assets Net

Deferred Tax Assets Liabilities Net

us-gaap:DeferredTaxAssetsLiabilitiesNet



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value44638026222119641-1826-145-267808
Percentage of DeferredTaxAssetsLiabilitiesNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.51.41.00.80.70.1-0.60.0-0.5-0.93.5

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value53357056252150944843440443945230729836837955456457657962516731755167815171531157314461230117411581174916937935946721102210591040807124712451274439420
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.81.92.01.71.71.71.71.51.60.01.21.11.41.42.12.22.22.22.36.16.05.95.15.35.04.84.14.03.93.93.03.23.03.12.43.63.53.52.85.35.25.51.91.8

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value2532
Percentage of OtherAssetsNoncurrent4.75.6
Percentage of Assets0.10.1
Percentage of Assets aon:AonCorporation0.10.1

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value3235283030372835
Percentage of OtherAssetsNoncurrent5.66.25.45.96.78.56.911.4
Percentage of Assets0.10.10.10.10.10.10.10.1
Percentage of Assets srt:GuarantorSubsidiaries0.10.10.10.10.10.10.10.2

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value508538525492478417396375271
Percentage of OtherAssetsNoncurrent95.394.493.494.493.993.191.292.888.3
Percentage of Assets1.71.81.91.71.61.61.51.41.0
Percentage of Assets srt:NonGuarantorSubsidiaries1.01.11.11.01.01.00.90.80.6

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value02111111
Percentage of OtherAssetsNoncurrent0.00.40.20.20.20.20.20.3
Percentage of Assets0.00.00.00.00.00.00.00.0
Percentage of Assets srt:ParentCompany0.00.00.00.00.00.00.00.0

Liabilities Current

us-gaap:LiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value17111155711485115481145371329612643138431365812755124741337512970124951136612697127931308613541148391411615014138561604015581154111519115195152611535013954152001425213760127651398713259129491181914138127761264012803
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets56.553.052.751.949.950.349.450.949.048.948.149.248.146.945.047.647.748.249.850.849.750.448.150.551.850.951.850.550.850.447.349.347.146.644.445.944.544.750.659.055.655.155.8

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value1758813714
Percentage of LiabilitiesCurrent102.888.1
Percentage of Assets58.146.6
Percentage of Assets aon:AonCorporation73.557.2

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value612055
Percentage of LiabilitiesCurrent0.413.2
Percentage of Assets0.27.0
Percentage of Assets aon:AonGlobalHoldingsLimited0.716.7

aon:AonUK



Period End2020-03-312019-12-31
Value23512503
Percentage of LiabilitiesCurrent13.716.1
Percentage of Assets7.88.5
Percentage of Assets aon:AonUK25.224.8

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value1371416676150431361411834149351383211249
Percentage of LiabilitiesCurrent88.1112.397.293.789.0118.199.988.2
Percentage of Assets46.659.250.546.744.858.350.843.1
Percentage of Assets srt:GuarantorSubsidiaries57.262.557.957.054.658.053.149.9

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value162321556215521166671529114048138151593615383
Percentage of LiabilitiesCurrent94.999.9104.5107.7105.2105.7109.3115.1120.6
Percentage of Assets53.652.955.155.952.553.254.058.659.0
Percentage of Assets srt:NonGuarantorSubsidiaries30.932.932.734.332.232.130.633.534.5

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value25031985152993873722492125720
Percentage of LiabilitiesCurrent16.113.49.96.55.517.815.45.6
Percentage of Assets8.57.05.13.22.88.87.82.8
Percentage of Assets srt:ParentCompany24.820.515.99.48.120.919.57.5

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-19121-16208-19331-17758-15306-13323-18356-18050-14597
Percentage of LiabilitiesCurrent-111.7-104.1-130.2-114.7-105.3-100.2-145.2-130.4-114.4
Percentage of Assets-63.1-55.1-68.6-59.6-52.5-50.4-71.7-66.3-56.0
Percentage of Assets srt:ConsolidationEliminations28.331.234.732.629.327.732.731.528.9

Debt Current

us-gaap:DebtCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value188471211488444262517417994032993052926673362502516955621327123796678366079910777031206427802452291392286337163525024926103708410105
Percentage of DebtCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.22.44.12.81.50.92.92.91.41.11.21.12.51.31.00.92.62.14.94.23.42.62.32.53.62.34.11.42.71.51.01.30.91.10.60.21.71.72.61.50.40.00.5

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value1136600
Percentage of DebtCurrent60.384.3
Percentage of Assets3.82.0
Percentage of Assets aon:AonCorporation4.72.5

aon:AonUK



Period End2020-03-312019-12-31
Value696112
Percentage of DebtCurrent36.915.7
Percentage of Assets2.30.4
Percentage of Assets aon:AonUK7.41.1

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value60059927517502003390
Percentage of DebtCurrent84.352.232.641.10.027.042.40.0
Percentage of Assets2.02.10.90.60.00.81.20.0
Percentage of Assets srt:GuarantorSubsidiaries2.52.21.10.70.00.81.30.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value520303111299
Percentage of DebtCurrent2.80.00.30.00.70.40.10.1100.0
Percentage of Assets0.20.00.00.00.00.00.00.01.1
Percentage of Assets srt:NonGuarantorSubsidiaries0.10.00.00.00.00.00.00.00.7

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value1125465692482505404590
Percentage of DebtCurrent15.747.667.458.299.672.957.40.0
Percentage of Assets0.41.91.90.90.92.11.70.0
Percentage of Assets srt:ParentCompany1.15.65.92.52.75.04.20.0

Accounts Payable And Accrued Liabilities Current

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value154919391499136914791016616001447154519699625158814231332948514771373142017721447136813911805152814981499193115231423144018531519133914321832161115571544181012811192126915351560
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.16.65.34.65.138.56.25.35.50.036.96.15.24.935.65.85.15.36.55.34.74.96.15.34.75.06.45.24.74.86.15.14.34.76.25.65.15.26.25.55.05.56.76.8

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value4956
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent3.22.9
Percentage of Assets0.20.2
Percentage of Assets aon:AonCorporation0.20.2

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value01994
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent0.0102.8
Percentage of Assets0.06.8
Percentage of Assets aon:AonGlobalHoldingsLimited0.016.2

aon:AonUK



Period End2020-03-312019-12-31
Value13452157
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent86.8111.2
Percentage of Assets4.47.3
Percentage of Assets aon:AonUK14.421.4

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value564257750666736
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent2.92.84.25.10.04.14.60.4
Percentage of Assets0.20.10.20.30.00.30.20.1
Percentage of Assets srt:GuarantorSubsidiaries0.20.20.20.30.00.30.30.2

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value1393167517052057176210166186130403913
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent89.986.4113.7150.3119.1100.0116.3210.140.7
Percentage of Assets4.65.76.16.96.038.57.311.215.0
Percentage of Assets srt:NonGuarantorSubsidiaries2.73.53.64.23.723.24.16.48.8

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value21571171582351015161452574
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent111.278.142.523.70.094.8100.36.0
Percentage of Assets7.34.22.01.20.05.95.32.2
Percentage of Assets srt:ParentCompany21.412.16.13.50.014.113.36.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-1238-1949-1419-1327-7090-1843-3112-2562
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent-79.9-100.5-94.7-96.9-47.90.0-115.2-215.1-26.6
Percentage of Assets-4.1-6.6-5.0-4.5-2.40.0-7.2-11.4-9.8
Percentage of Assets srt:ConsolidationEliminations1.83.72.52.41.4-0.03.35.45.1

Other Accrued Liabilities Current

us-gaap:OtherAccruedLiabilitiesCurrent



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
Value572513537504516602706723479420421447378402442372402331401394364314281307261247241
Percentage of OtherAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.91.71.91.71.82.32.82.71.71.61.61.61.41.51.81.41.51.21.51.31.31.11.01.00.90.80.8

Accrued Income Taxes Current

us-gaap:AccruedIncomeTaxesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value196931521331588316251641395371254577874676194824896696115140184155
Percentage of AccruedIncomeTaxesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.60.30.50.40.50.30.10.10.60.52.14.60.20.30.30.30.20.30.00.10.30.20.30.40.50.60.5

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value12771086116311971220936988112197288387012892078773873929872902820811845865788853957967906764769795831801733739753676618604584383350334260314
Percentage of OtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.23.74.14.04.23.53.94.13.50.03.35.07.62.93.33.73.33.43.03.02.93.02.63.03.03.23.02.62.62.62.72.72.42.42.52.42.02.02.01.61.51.51.11.4

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value8280
Percentage of OtherLiabilitiesCurrent6.47.4
Percentage of Assets0.30.3
Percentage of Assets aon:AonCorporation0.30.3

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value8079788169646264
Percentage of OtherLiabilitiesCurrent7.46.86.56.67.46.55.57.4
Percentage of Assets0.30.30.30.30.30.20.20.2
Percentage of Assets srt:GuarantorSubsidiaries0.30.30.30.30.30.20.20.3

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value119510061084111911398679241059790
Percentage of OtherLiabilitiesCurrent93.692.693.293.593.492.693.594.590.8
Percentage of Assets3.93.43.83.83.93.33.63.93.0
Percentage of Assets srt:NonGuarantorSubsidiaries2.32.12.32.32.42.02.02.21.8

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value000000016
Percentage of OtherLiabilitiesCurrent0.00.00.00.00.00.00.01.8
Percentage of Assets0.00.00.00.00.00.00.00.1
Percentage of Assets srt:ParentCompany0.00.00.00.00.00.00.00.2

Long Term Debt Noncurrent

us-gaap:LongTermDebtNoncurrent



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
Value6227662761206740599059935665565956975667566256315610586959105907590251754799482447104799484051553669368633524012377037134111409841684155441544794409401431461601201319981872
Percentage of LongTermDebtNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets20.622.521.722.620.622.722.120.820.521.721.820.720.822.123.422.122.019.117.616.516.616.116.816.212.212.211.413.312.612.213.913.313.814.115.414.714.813.813.56.78.88.78.2

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value24052404
Percentage of LongTermDebtNoncurrent38.636.3
Percentage of Assets7.98.2
Percentage of Assets aon:AonCorporation10.110.0

aon:AonUK



Period End2020-03-312019-12-31
Value38224223
Percentage of LongTermDebtNoncurrent61.463.7
Percentage of Assets12.614.4
Percentage of Assets aon:AonUK40.941.8

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value24041907250617621762141614151415
Percentage of LongTermDebtNoncurrent36.331.237.229.429.425.025.025.0
Percentage of Assets8.26.88.46.06.75.55.25.4
Percentage of Assets srt:GuarantorSubsidiaries10.07.19.67.48.15.55.46.3

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value0.00.00.00.00.00.00.01000000.01000000.0
Percentage of LongTermDebtNoncurrent0.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.0
Percentage of Assets srt:NonGuarantorSubsidiaries0.00.00.00.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value42234213423442284231424942434251
Percentage of LongTermDebtNoncurrent63.768.862.870.670.675.075.075.0
Percentage of Assets14.415.014.214.516.016.615.616.3
Percentage of Assets srt:ParentCompany41.843.544.142.546.439.538.944.4

Deferred Tax Liabilities Noncurrent

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent

aon:TheNetherlandsAndCanada, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value117111140146
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent100.0100.0100.0100.0
Percentage of Assets0.40.40.50.5
Percentage of Assets aon:TheNetherlandsAndCanada us-gaap:PensionPlansDefinedBenefit0.00.00.00.0

country:GB, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value19162034
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent16.214.414.323.3
Percentage of Assets0.10.10.10.1
Percentage of Assets country:GB us-gaap:PensionPlansDefinedBenefit0.00.00.00.0

country:US, us-gaap:PensionPlansDefinedBenefit



Period End2019-12-312018-12-312017-12-312016-12-31
Value1076103511541175
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent919.7932.4824.3804.8
Percentage of Assets3.73.94.44.4
Percentage of Assets country:US us-gaap:PensionPlansDefinedBenefit0.00.00.00.0

Minority Interest

us-gaap:MinorityInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value917469778768667384657266725760626657595866605759605056595443565858424667645552505552105
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.30.30.20.30.30.30.30.30.30.20.30.20.30.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.10.20.20.20.10.20.20.20.20.20.20.20.20.5

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value917469778768667365
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.30.30.20.30.30.30.30.30.2
Percentage of Assets srt:NonGuarantorSubsidiaries0.20.20.10.20.20.20.10.20.1

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-012017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value93087795392497310971090108811051099110284685873384475976783876910911140113187414221289124893213991340133810361326133213631024174317921798115487610239438711038
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.13.03.43.13.34.24.34.04.00.04.23.33.22.73.23.02.93.12.84.03.94.02.94.94.14.13.14.84.54.53.44.54.34.53.56.15.96.04.03.84.34.13.84.5

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value115113
Percentage of OtherLiabilitiesNoncurrent12.412.9
Percentage of Assets0.40.4
Percentage of Assets aon:AonCorporation0.50.5

aon:AonUK



Period End2020-03-312019-12-31
Value21
Percentage of OtherLiabilitiesNoncurrent0.20.1
Percentage of Assets0.00.0
Percentage of Assets aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value11310710611511510510491
Percentage of OtherLiabilitiesNoncurrent12.911.211.511.810.59.69.68.3
Percentage of Assets0.40.40.40.40.40.40.40.3
Percentage of Assets srt:GuarantorSubsidiaries0.50.40.40.50.50.40.40.4

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value8137638438158549799829821000
Percentage of OtherLiabilitiesNoncurrent87.487.088.588.287.889.290.190.390.7
Percentage of Assets2.72.63.02.72.93.73.83.63.8
Percentage of Assets srt:NonGuarantorSubsidiaries1.51.61.81.71.82.22.22.12.2

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value133433211
Percentage of OtherLiabilitiesNoncurrent0.10.30.30.40.30.30.21.0
Percentage of Assets0.00.00.00.00.00.00.00.0
Percentage of Assets srt:ParentCompany0.00.00.00.00.00.00.00.1

Stockholders Equity

us-gaap:StockholdersEquity



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
Value3169337534923836477541514262454553014583517554875754547554345499528161065883639863656571721577007946814575347559757977628305815283588078823383988423825157925428540253795310
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets10.511.512.412.916.415.716.616.719.017.620.020.221.320.621.520.619.722.521.621.922.422.125.024.226.426.925.725.125.225.528.126.527.627.328.627.528.328.524.822.723.523.423.1

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value-4818-957
Percentage of StockholdersEquity-152.0-28.4
Percentage of Assets-15.9-3.3
Percentage of Assets aon:AonCorporation-20.1-4.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-31
Value894010249
Percentage of StockholdersEquity282.1303.7
Percentage of Assets29.534.9
Percentage of Assets aon:AonGlobalHoldingsLimited99.383.3

aon:AonIreland



Period End2020-03-312019-12-31
Value31693375
Percentage of StockholdersEquity100.0100.0
Percentage of Assets10.511.5
Percentage of Assets aon:AonIreland100.0100.0

aon:AonUK



Period End2020-03-312019-12-31
Value31693375
Percentage of StockholdersEquity100.0100.0
Percentage of Assets10.511.5
Percentage of Assets aon:AonUK33.933.4

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-957-725-424-355-897-37192619
Percentage of StockholdersEquity-28.4-20.8-11.1-7.4-21.6-8.720.40.4
Percentage of Assets-3.3-2.6-1.4-1.2-3.4-1.43.40.1
Percentage of Assets srt:GuarantorSubsidiaries-4.0-2.7-1.6-1.5-4.1-1.43.60.1

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value333722836929137290842920227498289442924326793
Percentage of StockholdersEquity1053.1840.6834.4758.2611.6662.4679.1643.4584.6
Percentage of Assets110.296.5103.497.6100.2104.1113.1107.4102.7
Percentage of Assets srt:NonGuarantorSubsidiaries63.560.061.359.861.562.864.161.460.2

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value33753492383647754151426245454583
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.512.412.916.415.716.616.717.6
Percentage of Assets srt:ParentCompany33.436.040.048.045.539.641.647.9

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value-40663-27412-28412-28660-28847-26601-28573-30169-26812
Percentage of StockholdersEquity-1283.1-812.2-813.6-747.1-604.1-640.8-670.4-663.8-585.0
Percentage of Assets-134.3-93.2-100.9-96.2-99.0-100.7-111.6-110.8-102.8
Percentage of Assets srt:ConsolidationEliminations60.152.751.052.755.355.351.052.653.0

Common Stock Value

us-gaap:CommonStockValue



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
Value22222222223333333333333333333333386386386386386386363363363363362
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.01.31.31.31.31.31.31.61.51.61.61.6

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value1455125414361669255520932042229527472302291435743934380737023784360041174015440546124605471849825403573155075805584459336179630287708594837782338039786177007605750073356816
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 Assets4.84.35.15.68.87.98.08.49.98.811.213.114.614.314.714.213.415.214.815.116.215.516.415.718.018.918.819.319.519.520.920.529.029.129.127.027.027.133.031.732.731.929.7

Treasury Stock Value

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value-4409-4033-4030-3837-3740-3909-3632-3524-3191-3496-3412-3677-3750-3912-3793-3722-3710-3423-3453-3236-3427-3134-2518-2218-2320-2374-2636-2809-2775-2610-2250-2432-2239-2370-1900-1698-1714-1917-1741-1961-1871-1675-1462
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-14.6-13.7-14.3-12.9-12.8-14.8-14.2-12.9-11.5-13.4-13.2-13.5-13.9-14.7-15.0-13.9-13.8-12.6-12.7-11.1-12.1-10.5-8.7-7.0-7.7-7.8-9.0-9.3-9.2-8.6-7.6-7.9-7.4-8.0-6.6-5.6-5.8-6.6-7.5-8.2-8.1-7.3-6.4

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
Value33867280228774711562273140381-147260240851711491273934710229136759550344-1154-15582464553
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 Revenues10.523.333.711.02.425.723.910.74.513.1-6.311.010.126.125.917.89.828.425.98.24.823.019.111.8-0.41.9-0.521.124.430.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-512-34
Percentage of NetCashProvidedByUsedInOperatingActivities-151.5-45.9
Percentage of Revenues-15.9-1.1
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value3648529
Percentage of NetCashProvidedByUsedInOperatingActivities1079.3714.9
Percentage of Revenues113.316.8
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value1561-11
Percentage of NetCashProvidedByUsedInOperatingActivities461.8-14.9
Percentage of Revenues48.5-0.3
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-22-8-76-34-476-103-44626-4960
Percentage of NetCashProvidedByUsedInOperatingActivities-3.3-1.0-26.5-45.9-66.9-18.3-16.1447.1-130.2-0.0
Percentage of Revenues-0.8-0.3-2.9-1.1-17.2-4.4-1.720.3-17.10.0
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value852830888511179135014994822771024-69
Percentage of NetCashProvidedByUsedInOperatingActivities252.1123.5110.7178.0241.9189.9266.7176.6197.9268.846.9
Percentage of Revenues26.528.837.319.65.748.763.818.89.035.2-2.9
Percentage of Revenues srt:NonGuarantorSubsidiaries26.528.837.319.65.748.763.818.89.035.2-2.9

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-76-10377-111718-17-105-212922-17
Percentage of NetCashProvidedByUsedInOperatingActivities-11.3-1.2131.4-14.9241.6-3.0-38.5-15.0766.911.6
Percentage of Revenues-2.6-0.414.5-0.362.0-0.7-4.1-0.7100.4-0.7
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-5211-60-68-525-60-1881-817-60-742-3069-61
Percentage of NetCashProvidedByUsedInOperatingActivities-1541.7-8.9-8.5-182.9-81.1-264.6-145.4-22.0-530.0-805.541.5
Percentage of Revenues-161.9-2.1-2.9-20.1-1.9-67.9-34.8-2.3-24.0-105.5-2.6
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.0

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-4382-9-195-27-53-95-1673462651033147613-583-287115-1994815-2032-283-316-102156-62222-257-323-636
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 Revenues-13.60.1-0.4-7.5-0.9-1.9-4.0-6.511.29.144.162.30.5-17.9-10.54.2-7.11.50.5-7.20.1-8.6-11.0-3.55.3-2.17.8-9.3-17.0-34.5

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-568
Percentage of NetCashProvidedByUsedInInvestingActivities12.8-29.6
Percentage of Revenues-1.70.3
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-51872
Percentage of NetCashProvidedByUsedInInvestingActivities118.3-266.7
Percentage of Revenues-16.12.3
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value-4500
Percentage of NetCashProvidedByUsedInInvestingActivities102.7-0.0
Percentage of Revenues-14.00.0
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value3143-878-12-4-6836011191110
Percentage of NetCashProvidedByUsedInInvestingActivities1550.0-477.844.6-29.622.64.240.7104.0422.3107.5
Percentage of Revenues1.11.8-3.30.3-0.4-0.2-2.711.738.547.4
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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-382128-53-108-35867-91-99-14-297-77
Percentage of NetCashProvidedByUsedInInvestingActivities87.26400.0588.955.4129.6-1635.895.859.3-4.0-112.1-7.5
Percentage of Revenues-11.94.4-2.2-4.1-1.131.3-3.9-3.9-0.5-10.2-3.3
Percentage of Revenues srt:NonGuarantorSubsidiaries-11.94.4-2.2-4.1-1.131.3-3.9-3.9-0.5-10.2-3.3

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0000-10-11-1-210
Percentage of NetCashProvidedByUsedInInvestingActivities0.0-0.0-0.0-0.01.9-0.06.6-0.3-7.90.0
Percentage of Revenues0.00.00.00.0-0.00.0-0.4-0.0-0.70.0
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value968-157100-9070111-5360
Percentage of NetCashProvidedByUsedInInvestingActivities-221.0-7850.0-11.1-0.0-0.01711.3-0.0-6.60.3-202.30.0
Percentage of Revenues30.1-5.40.00.00.0-32.70.00.40.0-18.40.0
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.0

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
Value82-525-736-92-140-444-457-135-663-617-878-1512-258-271-371-640-4-979-582-33-95-430-254-189-260120-166341713
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 Revenues2.5-18.2-30.9-3.5-4.5-16.0-19.5-5.3-21.5-21.2-37.5-63.9-10.8-8.3-13.5-23.1-0.1-29.8-21.2-1.2-3.3-13.0-8.8-6.5-8.84.1-5.81.20.90.7

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-1509-90
Percentage of NetCashProvidedByUsedInFinancingActivities-1840.264.3
Percentage of Revenues-46.9-2.9
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-3094-601
Percentage of NetCashProvidedByUsedInFinancingActivities-3773.2429.3
Percentage of Revenues-96.1-19.1
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value-111111
Percentage of NetCashProvidedByUsedInFinancingActivities-1354.9-7.9
Percentage of Revenues-34.50.3
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value732124788-90-577-893436-907-1209-675
Percentage of NetCashProvidedByUsedInFinancingActivities-139.4-16.8-856.564.3130.0195.4-323.0136.8195.976.9
Percentage of Revenues25.45.230.2-2.9-20.8-38.017.0-29.4-41.6-28.8
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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-1309-1020-845-410-193-2000-1667-270-434-71490
Percentage of NetCashProvidedByUsedInFinancingActivities-1596.3194.3114.8445.7137.9450.5364.8200.065.5115.7-10.3
Percentage of Revenues-40.7-35.4-35.5-15.7-6.1-72.2-71.0-10.5-14.0-24.53.8
Percentage of Revenues srt:NonGuarantorSubsidiaries-40.7-35.4-35.5-15.7-6.1-72.2-71.0-10.5-14.0-24.53.8

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7610-37711-17171711621-290017
Percentage of NetCashProvidedByUsedInFinancingActivities-14.5-1.4409.8-7.9386.7-3.7-85.9-3.2470.0-1.9
Percentage of Revenues2.60.4-14.50.3-62.00.74.50.7-99.70.7
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7105-313-25-9313238502086-4176574206-310
Percentage of NetCashProvidedByUsedInFinancingActivities8664.659.63.4101.1-94.3-867.1-456.5308.9-99.1-681.735.3
Percentage of Revenues220.7-10.8-1.1-3.64.2139.088.8-16.321.3144.6-13.2
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.0

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
Value33867280228774711562273140381-147260240851711491273934710229136759550344-1154-15582464553
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 Revenues10.523.333.711.02.425.723.910.74.513.1-6.311.010.126.125.917.89.828.425.98.24.823.019.111.8-0.41.9-0.521.124.430.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-512-34
Percentage of NetCashProvidedByUsedInOperatingActivities-151.5-45.9
Percentage of Revenues-15.9-1.1
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value3648529
Percentage of NetCashProvidedByUsedInOperatingActivities1079.3714.9
Percentage of Revenues113.316.8
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value1561-11
Percentage of NetCashProvidedByUsedInOperatingActivities461.8-14.9
Percentage of Revenues48.5-0.3
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-22-8-76-34-476-103-44626-4960
Percentage of NetCashProvidedByUsedInOperatingActivities-3.3-1.0-26.5-45.9-66.9-18.3-16.1447.1-130.2-0.0
Percentage of Revenues-0.8-0.3-2.9-1.1-17.2-4.4-1.720.3-17.10.0
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value852830888511179135014994822771024-69
Percentage of NetCashProvidedByUsedInOperatingActivities252.1123.5110.7178.0241.9189.9266.7176.6197.9268.846.9
Percentage of Revenues26.528.837.319.65.748.763.818.89.035.2-2.9
Percentage of Revenues srt:NonGuarantorSubsidiaries26.528.837.319.65.748.763.818.89.035.2-2.9

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-76-10377-111718-17-105-212922-17
Percentage of NetCashProvidedByUsedInOperatingActivities-11.3-1.2131.4-14.9241.6-3.0-38.5-15.0766.911.6
Percentage of Revenues-2.6-0.414.5-0.362.0-0.7-4.1-0.7100.4-0.7
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-5211-60-68-525-60-1881-817-60-742-3069-61
Percentage of NetCashProvidedByUsedInOperatingActivities-1541.7-8.9-8.5-182.9-81.1-264.6-145.4-22.0-530.0-805.541.5
Percentage of Revenues-161.9-2.1-2.9-20.1-1.9-67.9-34.8-2.3-24.0-105.5-2.6
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss

Profit Loss

us-gaap:ProfitLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value79138222828767635315358610-12192778305459314280327590303188341467315313336360264252272307210254249280208267255241147158186218134155285
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues24.613.29.611.021.512.76.52.319.7-0.48.232.912.814.111.410.111.717.911.16.712.014.210.910.711.411.29.48.79.39.97.79.08.89.47.69.59.28.38.28.39.810.57.58.215.4

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value604513
Percentage of ProfitLoss76.475.9
Percentage of Revenues18.816.3
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value605600
Percentage of ProfitLoss76.588.8
Percentage of Revenues18.819.1
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonIreland



Period End2020-03-312019-03-31
Value7730
Percentage of ProfitLoss97.70.0
Percentage of Revenues24.00.0
Percentage of Revenues aon:AonIreland0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value773661
Percentage of ProfitLoss97.797.8
Percentage of Revenues24.021.0
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-95-3627513-103-36415582-270-216531
Percentage of ProfitLoss-24.9-15.89.475.9-29.2-237.925.995.42250.0-112.568.3
Percentage of Revenues-3.3-1.51.016.3-3.7-15.50.618.8-9.3-9.222.4
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value10454584435221423553-783861439133931514
Percentage of ProfitLoss132.1119.9194.3181.9210.5156.7-51.0665.5235.9-1108.348.4194.6
Percentage of Revenues32.515.918.620.045.320.0-3.315.146.64.64.063.9
Percentage of Revenues srt:NonGuarantorSubsidiaries32.515.918.620.045.320.0-3.315.146.64.64.063.9

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value36524427066135314566591-19185759
Percentage of ProfitLoss95.5107.094.197.8100.094.8113.896.9158.396.497.6
Percentage of Revenues12.710.310.421.012.76.22.619.1-0.77.932.1
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-3009-346-423-532-1921-450450-409-2002144130-2026
Percentage of ProfitLoss-380.4-90.6-185.5-185.4-284.2-127.5294.1-705.2-328.2-1200.067.7-260.4
Percentage of Revenues-93.5-12.0-17.8-20.4-61.1-16.219.2-16.0-64.85.05.6-85.6
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest



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
Value1961017861016779147781268101386911111198
Percentage of ProfitLoss2.42.63.52.52.33.917.22.6-58.33.61.24.61.52.22.93.71.02.65.33.81.71.92.93.34.04.43.54.3
Percentage of Revenues0.60.30.40.50.30.30.40.50.20.30.40.60.20.30.30.40.20.30.40.50.20.20.30.40.40.40.30.4
Percentage of Revenues us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



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
Value77222227765934514748594-19185769291502307272315584295178328459309304325261238246178
Percentage of ProfitLoss97.697.496.597.597.796.182.897.4158.396.498.895.4109.497.897.196.399.097.494.796.298.398.197.196.796.095.696.595.7
Percentage of Revenues24.09.310.621.012.56.31.919.2-0.77.932.512.215.411.29.811.317.810.86.311.513.910.710.411.09.08.48.99.3
Percentage of Revenues us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Depreciation Depletion And Amortization

Increase Decrease In Other Operating Capital Net

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet



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-1418942-58-74137162-263-38-316962-9233-2713-6929-3-125-508517-21-6219594117
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In 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-4382-9-195-27-53-95-1673462651033147613-583-287115-1994815-2032-283-316-102156-62222-257-323-636
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 Revenues-13.60.1-0.4-7.5-0.9-1.9-4.0-6.511.29.144.162.30.5-17.9-10.54.2-7.11.50.5-7.20.1-8.6-11.0-3.55.3-2.17.8-9.3-17.0-34.5

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-568
Percentage of NetCashProvidedByUsedInInvestingActivities12.8-29.6
Percentage of Revenues-1.70.3
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-51872
Percentage of NetCashProvidedByUsedInInvestingActivities118.3-266.7
Percentage of Revenues-16.12.3
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value-4500
Percentage of NetCashProvidedByUsedInInvestingActivities102.7-0.0
Percentage of Revenues-14.00.0
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value3143-878-12-4-6836011191110
Percentage of NetCashProvidedByUsedInInvestingActivities1550.0-477.844.6-29.622.64.240.7104.0422.3107.5
Percentage of Revenues1.11.8-3.30.3-0.4-0.2-2.711.738.547.4
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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-382128-53-108-35867-91-99-14-297-77
Percentage of NetCashProvidedByUsedInInvestingActivities87.26400.0588.955.4129.6-1635.895.859.3-4.0-112.1-7.5
Percentage of Revenues-11.94.4-2.2-4.1-1.131.3-3.9-3.9-0.5-10.2-3.3
Percentage of Revenues srt:NonGuarantorSubsidiaries-11.94.4-2.2-4.1-1.131.3-3.9-3.9-0.5-10.2-3.3

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0000-10-11-1-210
Percentage of NetCashProvidedByUsedInInvestingActivities0.0-0.0-0.0-0.01.9-0.06.6-0.3-7.90.0
Percentage of Revenues0.00.00.00.0-0.00.0-0.4-0.0-0.70.0
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value968-157100-9070111-5360
Percentage of NetCashProvidedByUsedInInvestingActivities-221.0-7850.0-11.1-0.0-0.01711.3-0.0-6.60.3-202.30.0
Percentage of Revenues30.1-5.40.00.00.0-32.70.00.40.0-18.40.0
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.0

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
Value595861495761686645584348346949525265838062776460556071563321
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

us-gaap:ConsolidatedEntities

aon:AonGlobalHoldingsLimited



Period End2020-03-31
Value0.0
Percentage of PaymentsToAcquirePropertyPlantAndEquipment0.0

aon:AonIreland



Period End2020-03-31
Value0.0
Percentage of PaymentsToAcquirePropertyPlantAndEquipment0.0

aon:AonUK



Period End2020-03-31
Value0.0
Percentage of PaymentsToAcquirePropertyPlantAndEquipment0.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value5958614957616866455843
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

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
Value82-525-736-92-140-444-457-135-663-617-878-1512-258-271-371-640-4-979-582-33-95-430-254-189-260120-166341713
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 Revenues2.5-18.2-30.9-3.5-4.5-16.0-19.5-5.3-21.5-21.2-37.5-63.9-10.8-8.3-13.5-23.1-0.1-29.8-21.2-1.2-3.3-13.0-8.8-6.5-8.84.1-5.81.20.90.7

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-1509-90
Percentage of NetCashProvidedByUsedInFinancingActivities-1840.264.3
Percentage of Revenues-46.9-2.9
Percentage of Revenues aon:AonCorporation0.00.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-3094-601
Percentage of NetCashProvidedByUsedInFinancingActivities-3773.2429.3
Percentage of Revenues-96.1-19.1
Percentage of Revenues aon:AonGlobalHoldingsLimited0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value-111111
Percentage of NetCashProvidedByUsedInFinancingActivities-1354.9-7.9
Percentage of Revenues-34.50.3
Percentage of Revenues aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value732124788-90-577-893436-907-1209-675
Percentage of NetCashProvidedByUsedInFinancingActivities-139.4-16.8-856.564.3130.0195.4-323.0136.8195.976.9
Percentage of Revenues25.45.230.2-2.9-20.8-38.017.0-29.4-41.6-28.8
Percentage of Revenues srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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-1309-1020-845-410-193-2000-1667-270-434-71490
Percentage of NetCashProvidedByUsedInFinancingActivities-1596.3194.3114.8445.7137.9450.5364.8200.065.5115.7-10.3
Percentage of Revenues-40.7-35.4-35.5-15.7-6.1-72.2-71.0-10.5-14.0-24.53.8
Percentage of Revenues srt:NonGuarantorSubsidiaries-40.7-35.4-35.5-15.7-6.1-72.2-71.0-10.5-14.0-24.53.8

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7610-37711-17171711621-290017
Percentage of NetCashProvidedByUsedInFinancingActivities-14.5-1.4409.8-7.9386.7-3.7-85.9-3.2470.0-1.9
Percentage of Revenues2.60.4-14.50.3-62.00.74.50.7-99.70.7
Percentage of Revenues srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7105-313-25-9313238502086-4176574206-310
Percentage of NetCashProvidedByUsedInFinancingActivities8664.659.63.4101.1-94.3-867.1-456.5308.9-99.1-681.735.3
Percentage of Revenues220.7-10.8-1.1-3.64.2139.088.8-16.321.3144.6-13.2
Percentage of Revenues srt:ConsolidationEliminations0.00.00.00.00.00.00.00.00.00.00.0

Proceeds From Issuance Of Long Term Debt

us-gaap:ProceedsFromIssuanceOfLongTermDebt



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
Value206011341359268887117941408174480830659992738673101110451857104915758709849312129119511507542975
Percentage of ProceedsFromIssuanceOfLongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value1603485
Percentage of ProceedsFromIssuanceOfLongTermDebt77.855.7

aon:AonUK



Period End2020-03-312019-03-31
Value457384
Percentage of ProceedsFromIssuanceOfLongTermDebt22.244.1

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value4974761855485132790114253750-2
Percentage of ProceedsFromIssuanceOfLongTermDebt43.835.069.055.774.064.081.746.40.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0-33-2221-2232
Percentage of ProceedsFromIssuanceOfLongTermDebt0.0-0.30.2-0.10.20.10.1-0.10.2100.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value64088083538446550632143100
Percentage of ProceedsFromIssuanceOfLongTermDebt56.464.831.144.125.935.918.453.30.00.0

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value1341108316301534694191914711323704181040950637676145717522389641210686845132891682971514079
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value1068310
Percentage of RepaymentsOfLongTermDebt79.644.7
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:AonCorporation0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value273384
Percentage of RepaymentsOfLongTermDebt20.455.3
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0751101231011771040111234900
Percentage of RepaymentsOfLongTermDebt0.046.166.044.761.370.784.149.60.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0000013029418
Percentage of RepaymentsOfLongTermDebt0.00.00.00.00.00.10.20.041.8100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations srt:NonGuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value10838795223847414282116100
Percentage of RepaymentsOfLongTermDebt100.053.934.055.338.629.115.98.70.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

Payments For Repurchase Of Common Stock

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value1341108316301534694191914711323704181040950637676145717522389641210686845132891682971514079
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value1068310
Percentage of RepaymentsOfLongTermDebt79.644.7
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:AonCorporation0.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value273384
Percentage of RepaymentsOfLongTermDebt20.455.3
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:AonUK0.00.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0751101231011771040111234900
Percentage of RepaymentsOfLongTermDebt0.046.166.044.761.370.784.149.60.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations srt:GuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0000013029418
Percentage of RepaymentsOfLongTermDebt0.00.00.00.00.00.10.20.041.8100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations srt:NonGuarantorSubsidiaries0.00.00.00.00.00.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value10838795223847414282116100
Percentage of RepaymentsOfLongTermDebt100.053.934.055.338.629.115.98.70.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations srt:ParentCompany0.00.00.00.00.00.00.00.00.00.0

Debt Instrument Interest Rate Stated Percentage

us-gaap:DebtInstrument

us-gaap:DebtInstrumentInterestRateStatedPercentage

aon:A2.20SeniorNotesdueNovember2020



Period End2020-03-31
Value0.022
Percentage of DebtInstrumentInterestRateStatedPercentage100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A2.20SeniorNotesdueNovember20200.0

aon:A2.875notesdue2026



Period End2020-03-31
Value0.02875
Percentage of DebtInstrumentInterestRateStatedPercentage130.7
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A2.875notesdue20260.0

aon:A3.50NotesdueJune2024



Period End2020-03-31
Value0.035
Percentage of DebtInstrumentInterestRateStatedPercentage159.1
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A3.50NotesdueJune20240.0

aon:A3.75SeniorNotesDueMay22029



Period End2020-03-31
Value0.0375
Percentage of DebtInstrumentInterestRateStatedPercentage170.5
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A3.75SeniorNotesDueMay220290.0

aon:A4.00SeniorNotesDueNovember2023



Period End2020-03-31
Value0.04
Percentage of DebtInstrumentInterestRateStatedPercentage181.8
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A4.00SeniorNotesDueNovember20230.0

aon:A4.50SeniorNotesDueDecember2028



Period End2020-03-31
Value0.045
Percentage of DebtInstrumentInterestRateStatedPercentage204.5
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A4.50SeniorNotesDueDecember20280.0

aon:A4.60SeniorNotesDueJune2044



Period End2020-03-31
Value0.046
Percentage of DebtInstrumentInterestRateStatedPercentage209.1
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A4.60SeniorNotesDueJune20440.0

aon:A5.00SeniorNotesDueSeptember2020



Period End2020-03-31
Value0.05
Percentage of DebtInstrumentInterestRateStatedPercentage227.3
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A5.00SeniorNotesDueSeptember20200.0

aon:A8.205NotesDueJanuary2027



Period End2020-03-31
Value0.08205
Percentage of DebtInstrumentInterestRateStatedPercentage373.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A8.205NotesDueJanuary20270.0

aon:SeniorNotes625PercentDue2040



Period End2020-03-31
Value0.0625
Percentage of DebtInstrumentInterestRateStatedPercentage284.1
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:SeniorNotes625PercentDue20400.0

us-gaap:DebtInstrument, us-gaap:LongtermDebtType

aon:A2.20SeniorNotesdueNovember2022, us-gaap:SeniorNotes



Period End2019-12-31
Value0.022
Percentage of DebtInstrumentInterestRateStatedPercentage0.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A2.20SeniorNotesdueNovember2022 us-gaap:SeniorNotes0.0

aon:A2.80SeniorNotesDueMarch2021, us-gaap:SeniorNotes



Period End2020-03-31
Value0.028
Percentage of DebtInstrumentInterestRateStatedPercentage127.3
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A2.80SeniorNotesDueMarch2021 us-gaap:SeniorNotes0.0

aon:A4.00SeniorNotesDueNovember2023, us-gaap:SeniorNotes



Period End2019-12-31
Value0.04
Percentage of DebtInstrumentInterestRateStatedPercentage0.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A4.00SeniorNotesDueNovember2023 us-gaap:SeniorNotes0.0

aon:A4.60SeniorNotesDueJune2044, us-gaap:SeniorNotes



Period End2019-12-31
Value0.046
Percentage of DebtInstrumentInterestRateStatedPercentage0.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A4.60SeniorNotesDueJune2044 us-gaap:SeniorNotes0.0

us-gaap:LongtermDebtType

aon:A3.75SeniorNotesDueMay22029



Period End2019-12-31
Value0.0375
Percentage of DebtInstrumentInterestRateStatedPercentage0.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A3.75SeniorNotesDueMay220290.0

aon:A4.00SeniorNotesDueNovember2023



Period End2019-12-31
Value0.04
Percentage of DebtInstrumentInterestRateStatedPercentage0.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A4.00SeniorNotesDueNovember20230.0

aon:A4.60SeniorNotesDueJune2044



Period End2019-12-31
Value0.046
Percentage of DebtInstrumentInterestRateStatedPercentage0.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A4.60SeniorNotesDueJune20440.0

aon:A5.00SeniorNotesDueSeptember2020



Period End2019-12-31
Value0.05
Percentage of DebtInstrumentInterestRateStatedPercentage0.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations aon:A5.00SeniorNotesDueSeptember20200.0

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value0.193-0.0070000000000000060.1960.1630.1570.106000000000000010.2011.6550.1590.8630.020.7690.001-0.0180000000000000160.1320.1640.1840.00.140.1220.1910.00400000000000000360.1910.1750.189-0.00500000000000000440.2510.2640.261
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

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

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

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

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod

us-gaap:PerformanceShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value00000000000000000000000001
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod100.00.00.00.0100.00.00.0100.0100.00.00.0100.0100.00.00.0100.0100.00.00.0100.0100.00.00.00.0100.0100.0

us-gaap:RestrictedStockUnitsRSU



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
Value000000000000000100010001112
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod88.70.00.00.0110.70.00.028233.390.00.00.08830.0114.10.00.011740.0109.80.00.07913.397.90.00.00.0140.4155.40.0

Share Based Compensation

us-gaap:ShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-06-302010-03-312009-06-302009-03-31
Value766572918912467707710566707810373708510175749081727310269557457665540
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Liabilities

us-gaap:DeferredTaxLiabilities



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value7105695791208118112261282126216211613466
Percentage of DeferredTaxLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Net

us-gaap:DeferredTaxAssetsNet



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value115694984114291377126711001268147613461274
Percentage of DeferredTaxAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Unrecognized Tax Benefits

us-gaap:UnrecognizedTaxBenefits



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-31
Value2992792802782181911641561181007786
Percentage of UnrecognizedTaxBenefits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Valuation Allowance

us-gaap:DeferredTaxAssetsValuationAllowance



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value200171136130175205127154219257186
Percentage of DeferredTaxAssetsValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value897929913959993
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-31
Value103110
Percentage of OperatingLeaseRightOfUseAsset11.511.8

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-31
Value110109112114
Percentage of OperatingLeaseRightOfUseAsset11.811.911.711.5

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value794819804847879
Percentage of OperatingLeaseRightOfUseAsset88.588.288.188.388.5

Cash And Cash Equivalents Period Increase Decrease

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value690790602581600656484487597756
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-12-312019-03-312018-12-31
Value1942271746862
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents28.1287.5124.3131.4

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-12-312019-03-312018-12-31
Value36000
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents5.20.00.00.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value16982619491537563575400672640793
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents246.1331.581.692.493.887.782.6138.0107.2104.9

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value-1238-4100-1419-1327-709-781-1843-3112-2646-2562
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents-179.4-519.0-235.7-228.4-118.2-119.1-380.8-639.0-443.2-338.9

aon:AccountsReceivableAllowanceForCreditLossForeignCurrencyTranslationAndOther



Period End2020-03-312019-09-302019-03-312018-09-30
Value3103
Percentage of AccountsReceivableAllowanceForCreditLossForeignCurrencyTranslationAndOther100.0100.00.0100.0

aon:AccountsReceivableAllowanceForCreditLossWriteoffNetOfRecoveries



Period End2020-03-312019-09-302019-03-312018-09-30
Value8-68-8
Percentage of AccountsReceivableAllowanceForCreditLossWriteoffNetOfRecoveries100.0100.0100.0100.0

us-gaap:CapitalizedContractCost

aon:CapitalizedContractCostAdditions

aon:CapitalizedCostToFulfillCustomerContracts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value318445326336346461332341370
Percentage of CapitalizedContractCostAdditions100.0100.0100.0100.0100.0100.0100.0100.0100.0

aon:CapitalizedCostToObtainCustomerContracts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1218141791616138
Percentage of CapitalizedContractCostAdditions3.84.04.35.12.63.54.83.82.2

us-gaap:CapitalizedContractCost

aon:CapitalizedContractCostForeignCurrencyAndOtherAdjustmentsNet

aon:CapitalizedCostToFulfillCustomerContracts



Period End2020-03-312019-03-31
Value-80
Percentage of CapitalizedContractCostForeignCurrencyAndOtherAdjustmentsNet100.00.0

aon:CapitalizedCostToObtainCustomerContracts



Period End2020-03-312019-03-31
Value-41
Percentage of CapitalizedContractCostForeignCurrencyAndOtherAdjustmentsNet50.00.0

us-gaap:ConsolidatedEntities

aon:EquityEarningsFromSubsidiaries

aon:AonCorporation



Period End2020-03-312019-03-31
Value862724
Percentage of EquityEarningsFromSubsidiaries100.0100.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value614619
Percentage of EquityEarningsFromSubsidiaries71.285.5

aon:AonIreland



Period End2020-03-312019-03-31
Value7730
Percentage of EquityEarningsFromSubsidiaries89.70.0

aon:AonUK



Period End2020-03-312019-03-31
Value759682
Percentage of EquityEarningsFromSubsidiaries88.194.2

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value122107301724136-4220670593122635
Percentage of EquityEarningsFromSubsidiaries0.00.00.0100.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value0-95-3627513-103-36415582-270-216531
Percentage of EquityEarningsFromSubsidiaries0.00.00.00.070.90.00.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value328330211682409-4217071833-36870
Percentage of EquityEarningsFromSubsidiaries0.00.00.094.20.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-3008-355-401-539-1919-442448-391-2005144130-2036
Percentage of EquityEarningsFromSubsidiaries-349.00.00.00.0-265.10.00.00.00.00.00.00.0

us-gaap:ConsolidatedEntities

aon:EquityOtherComprehensiveIncomeLossFromSubsidiaries

aon:AonCorporation



Period End2020-03-312019-03-31
Value-381115
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries100.0100.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-370139
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries97.1120.9

aon:AonIreland



Period End2020-03-312019-03-31
Value-3770
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries99.00.0

aon:AonUK



Period End2020-03-312019-03-31
Value-377167
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries99.0145.2

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value92-220-118115-221-134-3452853524571
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries0.00.00.0100.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value07-210-108139-254-124-338299-8925581
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries-0.00.00.00.0120.90.00.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value6-215-90167-285-106-351309-8426583
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries0.00.00.0145.20.00.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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
Value1505-105645316-4217603641034-893138-765-235
Percentage of EquityOtherComprehensiveIncomeLossFromSubsidiaries-395.00.00.00.0-366.10.00.00.00.00.00.00.0

aon:GainLossOnSaleofBusinessAndInvestmentsNet



Period End2020-03-312019-03-31
Value254
Percentage of GainLossOnSaleofBusinessAndInvestmentsNet100.0100.0

aon:IncomeLossBeforeEquityEarningsOfSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value79138222828767635315358610-12192778305459326308337
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-258-211
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries-32.6-31.2

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-9-19
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries-1.1-2.8

aon:AonUK



Period End2020-03-312019-03-31
Value14-21
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries1.8-3.1

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-217-143-274-211-239-322-191-123-363-338-104
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries-56.8-62.7-95.5-31.2-67.7-210.5-329.3-20.23025.0-176.0-13.4

srt:NonGuarantorSubsidiaries



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
Value1045553479495910656286371857403309983
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries132.1144.8210.1172.5134.6185.8186.9639.7140.5-3358.3160.9126.3

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value37-8659-21-56187-104-127-52221-111
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries9.7-37.720.6-3.1-15.9122.2-179.3-20.8433.3115.1-14.3

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-19-227-2-82-1830010
Percentage of IncomeLossBeforeEquityEarningsOfSubsidiaries-0.12.4-9.62.4-0.3-2.31.3-31.00.5-0.00.01.3

aon:IncomeLossFromContinuingOperationsBeforeIncomeTaxes



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value981441285343802421194-87718406200-186265571362335401702352214421581390380414353342368274351346292352356208244247178210343
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxes100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-306-253
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxes-31.2-31.5

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-11-24
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxes-1.1-3.0

aon:AonUK



Period End2020-03-312019-03-31
Value-3-26
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxes-0.3-3.2

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value13025736151083402279100840690
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxes132.7201.1179.3135.0207.2-320.7140.4203.0-48.4

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value-1-227-22-183010
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxes-0.1-7.72.0-0.21.020.70.40.0-5.4

us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aon:IncomeLossfromDiscontinuedOperationsExcludingGainLossonDisposalNetofTaxIncludingPortionAttributabletoNoncontrollingInterest

us-gaap:DiscontinuedOperationsHeldForSaleOrDisposedOfBySale, aon:TempoBusiness



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0-100-4-20-2-5-923407542
Percentage of IncomeLossfromDiscontinuedOperationsExcludingGainLossonDisposalNetofTaxIncludingPortionAttributabletoNoncontrollingInterest0.0100.00.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

aon:IncreaseDecreaseInFiduciaryLiabilities



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
Value1045544-77673711501034-1072237800249-560282-71104-1453467-11446-1059300-2361233-1549632106364706246
Percentage of IncreaseDecreaseInFiduciaryLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aon:IncreaseDecreaseInFiduciaryReceivables



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
Value808583-11003176091445-1649278605815-976327-337944-1442303-399196-911289-1731007-1551728-16542644-181
Percentage of IncreaseDecreaseInFiduciaryReceivables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:IntercompanyInterestExpenseIncome

aon:AonCorporation



Period End2020-03-312019-03-31
Value-113-116
Percentage of IntercompanyInterestExpenseIncome100.0100.0

aon:AonUK



Period End2020-03-312019-03-31
Value84
Percentage of IntercompanyInterestExpenseIncome-7.1-3.4

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-116-116-116-116-129-128-129-128-136-135-136
Percentage of IntercompanyInterestExpenseIncome0.00.00.0100.00.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value105106112113112125124126124132132132
Percentage of IntercompanyInterestExpenseIncome-92.90.00.00.0-96.60.00.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value104344434434
Percentage of IntercompanyInterestExpenseIncome0.00.00.0-3.40.00.00.00.00.00.00.0

us-gaap:ConsolidatedEntities

aon:IntercompanyOtherIncomeExpenseNet

aon:AonCorporation



Period End2020-03-312019-03-31
Value-128-94
Percentage of IntercompanyOtherIncomeExpenseNet100.0100.0

aon:AonUK



Period End2020-03-312019-03-31
Value8131
Percentage of IntercompanyOtherIncomeExpenseNet-63.3-33.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-90-9-164-99-140-251-3-5-131-271-16
Percentage of IntercompanyOtherIncomeExpenseNet0.00.00.0105.30.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value4737927681566645873-2069
Percentage of IntercompanyOtherIncomeExpenseNet-36.70.00.00.0-72.30.00.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value87-7013731-16245-61-5358291-53
Percentage of IntercompanyOtherIncomeExpenseNet0.00.00.0-33.00.00.00.00.00.00.00.0

us-gaap:DisposalGroupClassification

aon:NumberOfDispositions

us-gaap:DisposalGroupNotDiscontinuedOperations



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
Value1.02.02.03.01.01.02.01.00.05.00.01.03.01.00.02.02.04.01.00.02.0
Percentage of NumberOfDispositions100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.0100.00.0100.0100.0100.0100.00.0100.0

aon:OtherGeneralExpenses



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value342393310344346311336535318316317331308728713673693714685875723816756766727764803780778788778748765766488461468481528466
Percentage of OtherGeneralExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonUK



Period End2020-03-312019-03-31
Value260
Percentage of OtherGeneralExpenses7.60.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value116-4-7-7780-31-6
Percentage of OtherGeneralExpenses0.30.31.7-1.2-2.3-2.114.60.0-0.90.3-1.8

srt:NonGuarantorSubsidiaries



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
Value315387307335350317343455317317315333
Percentage of OtherGeneralExpenses92.198.599.097.4101.2101.9102.185.099.7100.399.4100.6

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value52301021214
Percentage of OtherGeneralExpenses1.30.60.90.00.30.00.40.30.60.31.2

aon:OtherNonoperatingIncomeExpenseOther



Period End2020-03-312019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302015-09-302014-09-30
Value10001-1-300001
Percentage of OtherNonoperatingIncomeExpenseOther100.00.00.00.0100.0100.0100.00.00.00.00.0100.0

aon:PaymentsForProceedsFromMarketableSecurities



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
Value38-42-55103-418-463-415-1112-11072545-94-169214-333227-18-88139-42191-84-34-18316-283-218-97193
Percentage of PaymentsForProceedsFromMarketableSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value28-9
Percentage of PaymentsForProceedsFromMarketableSecurities73.722.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-35-6278-99-1259-355-1113-1112
Percentage of PaymentsForProceedsFromMarketableSecurities83.3112.775.722.0112.5300.093.785.5100.1100.5

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value10-7725-32-184-6015
Percentage of PaymentsForProceedsFromMarketableSecurities26.316.7-12.724.378.0-12.5-200.06.314.5-0.1-0.5

aon:ProceedsPaymentTowardsIssuanceofSharesUnderIncentiveandSharebasedCompensationPlansNetofPaymentsRelatedtoTaxWithholdingforSharebasedCompensation



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value-11211-46-9811-41-10921-54-8517-22-6513-47-114
Percentage of ProceedsPaymentTowardsIssuanceofSharesUnderIncentiveandSharebasedCompensationPlansNetofPaymentsRelatedtoTaxWithholdingforSharebasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonUK



Period End2020-03-312019-03-31
Value-112-98
Percentage of ProceedsPaymentTowardsIssuanceofSharesUnderIncentiveandSharebasedCompensationPlansNetofPaymentsRelatedtoTaxWithholdingforSharebasedCompensation100.0100.0

aon:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodTax



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value8958810999477922138971515
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value7766898888
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodTax87.577.8120.075.0100.090.088.988.988.9200.0

us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value12-1201111-4
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodTax12.522.2-20.025.00.010.011.111.111.1-100.0

us-gaap:RestructuringCostAndReserve, us-gaap:RestructuringPlan

aon:RestructuringandRelatedCostIncurredContractTerminationCosts

aon:RealEstateRealizationCosts, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value18249211102031
Percentage of RestructuringandRelatedCostIncurredContractTerminationCosts100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

aon:TechnologyRationalization, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-12921310001
Percentage of RestructuringandRelatedCostIncurredContractTerminationCosts-66.7450.050.011.1150.09.10.00.00.033.3

us-gaap:OtherRestructuring, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value-81812337541
Percentage of RestructuringandRelatedCostIncurredContractTerminationCosts-44.4900.025.022.2150.027.3750.0200.033.3

us-gaap:AwardType

aon:ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuable

us-gaap:PerformanceShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value00000000000000000000000001
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShortTermDebtType

aon:ShortTermDebtAverageOutstandingAmountWeightedAverageInterestRate

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.0096-0.00159999999999999990.00150.0070.00490.83170.00790.0092-0.0050.00.00.00260.0012-0.00050.0002
Percentage of ShortTermDebtAverageOutstandingAmountWeightedAverageInterestRate100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0

us-gaap:ShareRepurchaseProgram

aon:TreasuryStockAcquiredAdditionalTransactionCosts

aon:ShareRepurchaseProgramOf2012



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
Value230611123245
Percentage of TreasuryStockAcquiredAdditionalTransactionCosts100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShareRepurchaseProgram

aon:TreasuryStockValueAcquiredCostMethodIncludingAssociatedAcquisitionCosts

aon:ShareRepurchaseProgramOf2012



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
Value46345335010561011983014025535027531035
Percentage of TreasuryStockValueAcquiredCostMethodIncludingAssociatedAcquisitionCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue



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
Value8172918912467707710766737510373708510175749081727310269557466
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:StatementEquityComponents

us-gaap:CommonStockIncludingAdditionalPaidInCapital



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
Value8172918912467707710766737510373708510175749081727310269557466
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 End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value7665729189124677077105676978103727185100757490817273102706869555055594774435766
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AwardType

aon:EmployeeStockPurchasePlan



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value4223213324324324223212222
Percentage of AllocatedShareBasedCompensationExpense5.32.82.23.43.01.43.94.52.95.14.22.84.74.02.74.42.82.72.92.91.52.93.64.03.6

us-gaap:PerformanceShares



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
Value1420283923802423166422211955252520502828213629283928271115132
Percentage of AllocatedShareBasedCompensationExpense18.430.838.942.925.864.535.832.920.861.032.830.424.453.434.735.223.550.037.337.823.344.440.338.438.240.039.715.927.326.03.6

us-gaap:RestrictedStockUnitsRSU



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
Value58434250634141465839424655454444614844446543414360404055373449
Percentage of AllocatedShareBasedCompensationExpense76.366.258.354.970.833.161.265.775.337.162.766.770.543.761.162.071.848.058.759.572.253.156.958.958.857.158.879.767.368.089.1

us-gaap:AmortizationOfIntangibleAssets



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-30
Value971019797101100282110100101460437072686777787980899087869899991051041049191913029272422
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value971019797101100282110100101460
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-30
Value000000001000000000000001110154555
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount0.00.00.0100.00.00.0100.00.0100.00.00.00.0100.00.00.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CapitalizedContractCost

us-gaap:CapitalizedContractCostAmortization

aon:CapitalizedCostToFulfillCustomerContracts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-4162542-299357439375305353432
Percentage of CapitalizedContractCostAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0

aon:CapitalizedCostToObtainCustomerContracts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-1277-1111111191110
Percentage of CapitalizedContractCostAmortization2.93.03.73.12.52.93.03.12.3

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-10018821-19-56172-3-110-159
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-2077-116
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect2077.0207.1

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value360
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect-36.0-0.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value741159625-116-1065-100032479
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect394.1757.1-3289.5207.1-619.233333.3-294.5-49.7

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-921-23-46-26-12175-27232-153
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect921.0-12.2-219.0136.821.4101.79066.7-29.196.2

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.00.00.00.00.00.00.0-1000000.0
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect0.00.0-0.0-0.00.0-0.0-0.00.6

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2862-530-92-6187210621269-466-84
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect-2862.0-281.9-438.13252.6-128.6617.4-42300.0423.652.8

us-gaap:CommonStockDividendsPerShareDeclared



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value0.440.440.440.40.40.40.36
Percentage of CommonStockDividendsPerShareDeclared100.0100.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiabilityRevenueRecognized



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value11714714495134139133115
Percentage of ContractWithCustomerLiabilityRevenueRecognized100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredIncomeTaxesAndTaxCredits



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-68-190-25-97-35-1192619019-225-2-17-22-823-140-9997-21259810131611-1214
Percentage of DeferredIncomeTaxesAndTaxCredits100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

country:GB



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-7-7-8-7-6-7-8-8-8-7-7-9
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

country:US



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-17-13-14-13-15-15-15-13-12-13-12-12
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses242.9185.7175.0185.7250.0214.3187.5162.5150.0185.7171.4133.3

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

country:GB



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302016-09-302016-06-30
Value0.00.00.01000000.01000000.00.00.00.00.00.01000000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.00.0100.0100.00.00.00.00.00.0100.0

country:US



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302016-09-302016-06-30
Value0.01000000.00.01000000.00.01000000.00.00.01000000.01000000.01000000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.00.0100.00.00.00.00.00.00.0100.0

us-gaap:DefinedBenefitPlanContributionsByEmployer



Period End2020-03-312019-09-302019-03-312018-09-30
Value352947138
Percentage of DefinedBenefitPlanContributionsByEmployer100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation

aon:OtherInternationalPlan



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
Value233733839243
Percentage of DefinedBenefitPlanContributionsByEmployer5.710.30.014.92.20.00.00.00.00.00.00.0

country:GB



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
Value21923232725232226161917
Percentage of DefinedBenefitPlanContributionsByEmployer5.765.50.048.919.60.00.00.00.00.00.00.0

country:US



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
Value3176171088175131356
Percentage of DefinedBenefitPlanContributionsByEmployer88.624.10.036.278.30.00.00.00.00.00.00.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

aon:OtherInternationalPlan



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
Value8910101111121311111212
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

country:GB



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
Value394648494650515049485865
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets487.5511.1480.0490.0418.2454.5425.0384.6445.5436.4483.3541.7

country:US



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
Value333434343636363435353939
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets412.5377.8340.0340.0327.3327.3300.0261.5318.2318.2325.0325.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanInterestCost

aon:OtherInternationalPlan



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
Value467767776677
Percentage of DefinedBenefitPlanInterestCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

country:GB



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
Value222627282629293130303743
Percentage of DefinedBenefitPlanInterestCost550.0433.3385.7400.0433.3414.3414.3442.9500.0500.0528.6614.3

country:US



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
Value212727272425252424242828
Percentage of DefinedBenefitPlanInterestCost525.0450.0385.7385.7400.0357.1357.1342.9400.0400.0400.0400.0

us-gaap:RetirementPlanSponsorLocation

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

aon:OtherInternationalPlan



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-1000-2-1-2-3-2-2-2-2
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0

country:GB



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-10-13-13-13-42-7-11-11-11-1449
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost1000.00.00.00.0200.0-200.0350.0366.7550.0550.0700.0-2450.0

country:US



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
Value577735432222
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost-500.00.00.00.0-150.0-500.0-200.0-100.0-100.0-100.0-100.0-100.0

us-gaap:Depreciation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value4148444040504047393940545461394156605657565961626059555331
Percentage of Depreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



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
Value414844404050404739394054
Percentage of Depreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

us-gaap:DerivativeGainLossOnDerivativeNet

us-gaap:ForeignExchangeContract, us-gaap:Nondesignated



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
Value-352-16-9-542-4-209-28-1-11-2-21215
Percentage of DerivativeGainLossOnDerivativeNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax

us-gaap:DiscontinuedOperationsHeldForSaleOrDisposedOfBySale, aon:TempoBusiness



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value000073018-245798000
Percentage of DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax0.00.00.00.0100.00.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax

us-gaap:DiscontinuedOperationsHeldForSaleOrDisposedOfBySale, aon:TempoBusiness



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value0-1-10-5-40-3-16-152657105675343
Percentage of DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax0.0100.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:DiscontinuedOperationTaxEffectOfDiscontinuedOperation

us-gaap:DiscontinuedOperationsHeldForSaleOrDisposedOfBySale, aon:TempoBusiness



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value00-10-1-20-1-11-631730251818
Percentage of DiscontinuedOperationTaxEffectOfDiscontinuedOperation0.00.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:DisposalGroupIncludingDiscontinuedOperationOperatingExpense

us-gaap:DiscontinuedOperationsHeldForSaleOrDisposedOfBySale, aon:TempoBusiness



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value011054031614156470507491466486
Percentage of DisposalGroupIncludingDiscontinuedOperationOperatingExpense0.0100.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302011-06-302010-09-302010-06-302009-09-302009-06-30
Value255125-2-30-1-1400-2-20635620119-12500100-1-8227
Percentage of DisposalGroupNotDiscontinuedOperationGainLossOnDisposal100.0100.0100.0100.0100.0100.0100.00.0100.0100.00.00.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.00.00.0100.00.0100.0100.0100.0100.0100.0

us-gaap:DividendsCommonStockCash



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
Value10210410796979898899092958787898782838485717273755350495141
Percentage of DividendsCommonStockCash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



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
Value10210410796979898899092958787898782838485717273755350495141
Percentage of DividendsCommonStockCash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectOfExchangeRateOnCashAndCashEquivalents



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-82-36-1937-42-13-8118-2257925-49-8711-17-112-4-39-54-1627-24510-2347-11
Percentage of EffectOfExchangeRateOnCashAndCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-82-36-1937-42-13-8118-2257
Percentage of EffectOfExchangeRateOnCashAndCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax



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
Value42-81711-119329-16-5-20-2-101221-17-316-72477-1519-4-524-2418-1824-4-2
Percentage of ForeignCurrencyTransactionGainLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:GainLossOnSaleOfInvestments



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-03-312009-09-30
Value-44-20-1310-27016-6-43-8-2-123-224-1-137-219-8101-11011
Percentage of GainLossOnSaleOfInvestments100.0100.0100.0100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312013-09-302013-06-302012-09-302012-06-302011-06-302011-03-312010-12-312010-06-302009-12-312009-09-302009-06-302009-03-31
Value-10-10069-216-29-48214075423525000-122-1-26563250
Percentage of IncomeLossFromDiscontinuedOperationsNetOfTax100.00.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



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-10-10069-216-29-4821
Percentage of IncomeLossFromDiscontinuedOperationsNetOfTax100.00.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:DiscontinuedOperationsHeldForSaleOrDisposedOfBySale, aon:TempoBusiness



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value0-10069-216-29-48214075423525
Percentage of IncomeLossFromDiscontinuedOperationsNetOfTax0.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312013-09-302013-06-302012-09-302012-06-302011-12-312010-06-302009-12-312009-09-302009-03-31
Value0.00.00.00.00.00.28-0.010.010.02-0.12-0.023.130.150.280.160.130.090.00.00.00.00.01-0.090.20.010.18
Percentage of IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare0.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.0

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312013-09-302013-06-302012-09-302012-06-302011-12-312010-06-302009-12-312009-09-302009-06-302009-03-31
Value0.00.00.00.00.00.28-0.010.00.02-0.11-0.013.130.150.280.150.130.090.00.00.00.00.01-0.090.20.010.010.17
Percentage of IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare0.00.00.00.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.0100.0

us-gaap:IncomeLossFromEquityMethodInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-30
Value11111111112366412344224156420355-26-142101
Percentage of IncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-312009-03-31
Value-275357194-125-454356164-56-43933314013-390341112-41-348502122-71-46632784-24-468-417-451-327-274-260
Percentage of IncreaseDecreaseInAccountsPayableAndAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

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
Value141-23-7-1081181717-17430-129-76031-56786-4-3118583-17927253-66-1472-6541586582
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:IncreaseDecreaseInClientFundsHeld



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
Value237-39324420541-411577-41195-566415-44330160-11164285-150-14811-632262-9627132262-427-396-512
Percentage of IncreaseDecreaseInClientFundsHeld100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

us-gaap:IncreaseDecreaseInDueToAffiliates

aon:AonCorporation



Period End2020-03-312019-03-31
Value-2044-265
Percentage of IncreaseDecreaseInDueToAffiliates100.0100.0

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-3094-601
Percentage of IncreaseDecreaseInDueToAffiliates151.4226.8

aon:AonUK



Period End2020-03-312019-03-31
Value-618305
Percentage of IncreaseDecreaseInDueToAffiliates30.2-115.1

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value235399-55-265-727-754123-933-1209-673
Percentage of IncreaseDecreaseInDueToAffiliates0.00.00.0100.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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-1349-995-828-370-172-1987-1659-253-142-701107
Percentage of IncreaseDecreaseInDueToAffiliates66.00.00.00.064.90.00.00.00.00.00.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1073454518305-1136327547418-2296876
Percentage of IncreaseDecreaseInDueToAffiliates0.00.00.0-115.10.00.00.00.00.00.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7105-313-25-9313238502086-4176574206-310
Percentage of IncreaseDecreaseInDueToAffiliates-347.60.00.00.0-49.80.00.00.00.00.00.0

us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations



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-41-29-35-38-54-36-139-31-5376-41-60-41112-4222-50-39-69-56-66-41-73-98-128-196-110-81-55-142
Percentage of IncreaseDecreaseInPensionAndPostretirementObligations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

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
Value543204-31019458116-360102269398-16963-38375-114-65-110315-173-10-49245-105-102-13-174-61-108-45-179
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:IncreaseDecreaseInRestructuringReserve



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-6065-447-259236-242-879990000-6-6-6-13-8-13-22-40-16-16-28
Percentage of IncreaseDecreaseInRestructuringReserve100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-30
Value102210111010202120222033333333445634787
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InformationTechnologyAndDataProcessing



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value1111311201261171211251231151241099888105999983
Percentage of InformationTechnologyAndDataProcessing100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



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
Value11113112012611712112512311512410998
Percentage of InformationTechnologyAndDataProcessing100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestPaidNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value51934912027942787587751
Percentage of InterestPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentIncomeInterestAndDividend



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value24112001471082313243433322321123446441327
Percentage of InvestmentIncomeInterestAndDividend100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value109
Percentage of InvestmentIncomeInterestAndDividend500.0450.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value10119914151514171811
Percentage of InvestmentIncomeInterestAndDividend250.01100.0900.0450.00.00.01500.0350.0242.9180.0137.5

srt:NonGuarantorSubsidiaries



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
Value1400000000402
Percentage of InvestmentIncomeInterestAndDividend700.00.00.00.00.00.00.00.00.057.10.025.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-22-6-10-8-7-14-15-14-10-14-8-5
Percentage of InvestmentIncomeInterestAndDividend-1100.0-150.0-1000.0-800.0-350.00.00.0-1400.0-250.0-200.0-80.0-62.5

us-gaap:LaborAndRelatedExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-302009-03-31
Value1522160113681501158416011392149416161752141914571461196616111688164918571644165316831848170717081751166617121725162016391661163416121597105011691163111911341014
Percentage of LaborAndRelatedExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-128
Percentage of LaborAndRelatedExpense-0.80.5

aon:AonUK



Period End2020-03-312019-03-31
Value1220
Percentage of LaborAndRelatedExpense0.81.3

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value6248-63112183
Percentage of LaborAndRelatedExpense0.40.10.30.5-0.40.20.10.10.11.30.2

srt:NonGuarantorSubsidiaries



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
Value152216001354147515561580137614781596157313851455
Percentage of LaborAndRelatedExpense100.099.999.098.398.298.798.998.998.889.897.699.9

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-51222202713151965258
Percentage of LaborAndRelatedExpense-0.30.91.51.31.70.91.01.23.71.80.5

us-gaap:LitigationCase

us-gaap:LossContingencyDamagesSoughtValue

aon:LyttletonPortCompanyLimited



Period End2019-12-312015-06-29
Value123184
Percentage of LossContingencyDamagesSoughtValue100.0100.0

us-gaap:LitigationCase, us-gaap:LitigationStatus

aon:ChristchurchCityCouncil, us-gaap:PendingLitigation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-03-312017-10-032017-09-30
Value315528333353365352385528381
Percentage of LossContingencyDamagesSoughtValue0.0429.30.00.00.00.00.00.00.0

us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship

us-gaap:NotionalAmountOfNonderivativeInstruments

us-gaap:NetInvestmentHedging



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-12-312018-09-30
Value1011015002802202500-36
Percentage of NotionalAmountOfNonderivativeInstruments100.0100.0100.0100.0100.0100.0100.0

us-gaap:NumberOfBusinessesAcquired



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value5.00.02.00.01.03.00.02.03.09.04.02.03.01.02.02.02.01.02.02.0
Percentage of NumberOfBusinessesAcquired100.00.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:NumberOfReportableSegments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value1.00.00.00.01.0
Percentage of NumberOfReportableSegments100.00.00.00.0100.0

us-gaap:OccupancyNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value7391768587879496938989868486868982
Percentage of OccupancyNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value54
Percentage of OccupancyNet6.84.6

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value64940000000
Percentage of OccupancyNet6.65.310.64.60.00.00.00.00.00.00.0

srt:NonGuarantorSubsidiaries



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
Value688572768387949693898986
Percentage of OccupancyNet93.293.494.789.495.4100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax

us-gaap:NetInvestmentHedging



Period End2020-03-312019-12-312019-09-302018-12-31
Value30293821
Percentage of OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value-403-215-121146-302-139-369277-21324461150-30510-239183-320-623-3298619
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value1-3-611-918822000
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-0.21.45.07.565.5-23.87.90.00.00.0

us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-395-208-103131-47-45424423660146
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax98.096.785.189.733.8123.088.196.798.497.3

us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-9-4-124-1-311814
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax2.21.99.92.70.70.84.03.31.62.7

us-gaap:DerivativeInstrumentRisk

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax

us-gaap:ForeignExchangeContract



Period End2020-03-312019-03-31
Value-114
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax100.0100.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax



Period End2019-12-312019-09-302019-06-302019-03-31
Value-2-4-3-5
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax100.0100.0100.0100.0

us-gaap:IncomeStatementLocation

aon:CompensationandBenefits



Period End2019-12-312019-09-302019-06-302019-03-31
Value-1000000.00.00.00.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax50.0-0.0-0.0-0.0

us-gaap:InterestExpense



Period End2019-12-312019-09-302019-06-302019-03-31
Value0.00.00.0-1000000.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax-0.0-0.0-0.020.0

us-gaap:Sales



Period End2019-12-312019-09-302019-06-302019-03-31
Value-1-4-3-4
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax50.0100.0100.080.0

us-gaap:OtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-312012-06-302012-03-31
Value-378-1-197-97171-275-111-339309-8227268163-121-71-12-28724-221190-293-619-30010254-34-165-196132
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value1124
Percentage of OtherComprehensiveIncomeLossNetOfTax-2.914.0

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-03-31
Value-390145
Percentage of OtherComprehensiveIncomeLossNetOfTax103.284.8

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



Period End2020-03-312019-03-31
Value12
Percentage of OtherComprehensiveIncomeLossNetOfTax-0.31.2

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest



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
Value-22-4022-3-6327-51-20000-4-1-1-100-2-23
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.00.00.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



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-22-4022-3-6327-5
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent



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
Value-376-3-193-97169-277-108-333306-8426573162-119-71-12-28730-217191-293-616-30010254171-32-165182-193131-20216203
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-370139
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent98.482.2

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value-370139
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent98.482.2

aon:AonIreland



Period End2020-03-312019-03-31
Value-3770
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.30.0

aon:AonUK



Period End2020-03-312019-03-31
Value-377167
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.398.8

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value7-210-108139-254-124-338299-8925581
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent-233.3108.8111.382.291.7114.8101.597.7106.096.2111.0

srt:NonGuarantorSubsidiaries



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-38898-435-208282-506-240-696594-49510154
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent103.2-3266.7225.4214.4166.9182.7222.2209.0194.158.3192.5211.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value6-215-90167-285-106-351309-8426583
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent-200.0111.492.898.8102.998.1105.4101.0100.0100.0113.7

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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
Value1506-114667309-4197683621052-896138-765-245
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent-400.53800.0-345.6-318.6-247.9-277.3-335.2-315.9-292.8-164.3-288.7-335.6

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value24171431-6212248182018
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent-6.4-8.8-14.418.357.4-36.615.76.827.411.1

us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-395-208-103131-47-45424423649146
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent105.1107.8106.277.543.5136.379.789.167.190.1

us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-5-2-871-114114-2
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent1.31.08.24.1-0.90.34.64.25.5-1.2

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-24203-17-14-319162-122-4837-18-20-18-148-18-51201-93-18-21-23330-26-18-26-24-18-23-7-18-21
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:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-13-22
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax54.271.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value86-10-10-2236-12-11-11124-7-8
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax42.458.871.471.039.6-19.49.022.9335.138.940.0

srt:NonGuarantorSubsidiaries



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-11117-7-4-95574-111-37-87-11-12
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax45.857.641.228.629.060.4119.491.077.1-235.161.160.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value-24-17-14-319162-122-4837-18-20-18-148-18-51201-93-18-21-23330-26-18-26-23
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value-56-2-87-31-114-1114-2-10-4-7-10-6-10-21-1413000
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.00.00.00.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value-22
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax40.028.6

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value10023-2-43032
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax16.7-0.0-0.028.6-100.0-200.0400.021.4-0.027.350.0

srt:NonGuarantorSubsidiaries



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-35-2-85-63311-182
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax60.083.3100.0100.071.4200.0300.0-300.078.6100.072.750.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-31
Value-5-2-87-31-114-1114-2-10-4-7-100-10-21
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0-0.0100.00.0100.0100.0

us-gaap:PaymentsForRepurchaseOfEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value4634533521055100198301402569511788
Percentage of PaymentsForRepurchaseOfEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonUK



Period End2020-03-312019-03-31
Value463100
Percentage of PaymentsForRepurchaseOfEquity100.0100.0

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
Value1021031041079697989889909295878789878283848571727375535049514141
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:ConsolidatedEntities

aon:AonUK



Period End2020-03-312019-03-31
Value10296
Percentage of PaymentsOfDividendsCommonStock100.0100.0

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value10310410796979898899092
Percentage of PaymentsOfDividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

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
Value33402401580212985723103466811516716-1032211538178522334733
Percentage of PaymentsToAcquireBusinessesNetOfCashAcquired100.00.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0.00.00.00.00.00.00.00.01000000.01000000.0
Percentage of PaymentsToAcquireBusinessesNetOfCashAcquired0.00.00.00.00.00.00.00.00.14.3

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value33402401580212985622
Percentage of PaymentsToAcquireBusinessesNetOfCashAcquired100.00.0100.00.0100.0100.00.0100.0100.099.995.7

us-gaap:PaymentsToAcquireOtherInvestments



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
Value43193446141529251192323917181514263201154103361012
Percentage of PaymentsToAcquireOtherInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value309
Percentage of PaymentsToAcquireOtherInvestments69.864.3

aon:AonGlobalHoldingsLimited



Period End2020-03-312019-03-31
Value5180
Percentage of PaymentsToAcquireOtherInvestments1204.70.0

aon:AonUK



Period End2020-03-312019-03-31
Value4500
Percentage of PaymentsToAcquireOtherInvestments1046.50.0

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value16271091119125410
Percentage of PaymentsToAcquireOtherInvestments84.279.421.764.373.365.548.045.544.443.5

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1338365410136513
Percentage of PaymentsToAcquireOtherInvestments30.215.823.578.335.726.734.552.054.555.656.5

srt:ParentCompany



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0000101112450
Percentage of PaymentsToAcquireOtherInvestments0.00.00.00.06.70.044.09.12722.20.0

us-gaap:ConsolidationItems

srt:ConsolidationEliminations



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-9680-100-10-11-1-2450
Percentage of PaymentsToAcquireOtherInvestments-2251.20.0-2.90.00.0-6.70.0-44.0-9.1-2722.20.0

us-gaap:PaymentsToMinorityShareholders



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-03-31
Value2220382314615015118269204200500-11
Percentage of PaymentsToMinorityShareholders100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.00.00.0100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value222038231461501511
Percentage of PaymentsToMinorityShareholders100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

us-gaap:PensionExpense



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-43-3-5-4-607-2112-9-9-8
Percentage of PensionExpense100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromDivestitureOfBusinessesNetOfCashDivested



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
Value3093616-2-92-15214195-231697151211410470110
Percentage of ProceedsFromDivestitureOfBusinessesNetOfCashDivested100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.00.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value3093616-2-92-1521
Percentage of ProceedsFromDivestitureOfBusinessesNetOfCashDivested100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities



Period End2020-03-312019-03-31
Value40-23
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.0

us-gaap:ConsolidatedEntities

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-03-31
Value40-23
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.0

us-gaap:ProceedsFromSaleAndMaturityOfOtherInvestments



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
Value6281921241761725144251281013197137313642183617667
Percentage of ProceedsFromSaleAndMaturityOfOtherInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConsolidatedEntities

aon:AonCorporation



Period End2020-03-312019-03-31
Value28
Percentage of ProceedsFromSaleAndMaturityOfOtherInvestments33.366.7

srt:GuarantorSubsidiaries



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1281883310119
Percentage of ProceedsFromSaleAndMaturityOfOtherInvestments42.942.150.066.719.542.950.058.844.064.3

srt:NonGuarantorSubsidiaries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value417311149414375715
Percentage of ProceedsFromSaleAndMaturityOfOtherInvestments66.7617.957.950.033.32295.157.150.041.22284.035.7

us-gaap:ProvisionForDoubtfulAccounts



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
Value9874839382556-6566113831443-5110
Percentage of ProvisionForDoubtfulAccounts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value-35-31-29-31-34-39-46-38-160-30-21-16-25-27-31-30-40-15-38-23-50
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-30-27-26-26-37-43-34-26-28-26
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax85.787.189.783.994.993.589.586.7133.3162.5

us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value00000000110
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-52.4-0.0

us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-5-4-3-5-2-3-4-4-410
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax14.312.910.316.15.16.510.513.319.0-62.5

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value-27-22-24-23-25-31-36-29-129-21-12-12-18-20-22-8-27-7-29-16-35
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-23-20-20-20-29-34-26-18-20-18
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax85.290.983.387.093.594.489.785.7166.7150.0

us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value00000000110
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-91.7-0.0

us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value-4-2-4-3-2-2-3-3-36
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax14.89.116.713.06.55.610.314.325.0-50.0

us-gaap:RestructuringCostAndReserve, us-gaap:RestructuringPlan

us-gaap:RestructuringAndRelatedCostIncurredCost

aon:AssetImpairments, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value752022810211
Percentage of RestructuringAndRelatedCostIncurredCost100.0100.0100.00.0100.0100.0100.0100.00.0100.0100.0

aon:RealEstateRealizationCosts, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value16359411103041
Percentage of RestructuringAndRelatedCostIncurredCost228.660.0250.00.0200.0550.0125.0300.00.0200.09.1

aon:TechnologyRationalization, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value1014411171281011127
Percentage of RestructuringAndRelatedCostIncurredCost142.9280.0200.00.0850.0600.0100.01000.00.0600.063.6

us-gaap:EmployeeSeverance, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value9497824311833334252102
Percentage of RestructuringAndRelatedCostIncurredCost1342.9180.03900.00.01550.0900.0412.53300.00.02600.0927.3

us-gaap:OtherRestructuring, aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value43323847655413627433234
Percentage of RestructuringAndRelatedCostIncurredCost614.3640.01900.00.03250.02700.01700.02700.00.01600.0309.1

us-gaap:RestructuringPlan

aon:A2017Plan



Period End2019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value1706312791119971957496102155
Percentage of RestructuringAndRelatedCostIncurredCost2428.61260.06350.00.05950.04850.02437.57400.00.05100.01409.1

us-gaap:RestructuringCharges



Period End2020-03-312019-03-312013-03-31
Value09126
Percentage of RestructuringCharges0.0100.0100.0

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod

us-gaap:RestrictedStockUnitsRSU



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
Value79000.055000.067000.056000.041000.040000.049000.046000.063000.049000.068000.0472000.050000.046000.0120000.0119000.094000.060000.098000.081000.049000.0105000.0164000.096000.0125000.0128000.0179000.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue

us-gaap:RestrictedStockUnitsRSU



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
Value146.03.04.03.0121.03.02.04.0105.01.00.01.091.01.02.01.078.01.03.03.064.02.02.04.050.044.044.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

us-gaap:PerformanceShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value160.01.00.0-1.0165.00.00.0-1.0135.00.00.0-1.0115.00.0-1.00.0101.00.00.00.096.00.00.00.081.058.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue100.0100.00.0100.0100.00.00.0100.0100.00.00.0100.0100.00.0100.00.0100.00.00.00.0100.00.00.00.0100.0100.0

us-gaap:RestrictedStockUnitsRSU



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
Value179.01.01.03.0170.01.00.0-4.0144.01.01.02.0119.00.00.02.099.0-1.00.01.097.00.00.01.083.060.047.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue111.9100.00.0-300.0103.00.00.0400.0106.70.00.0-200.0103.50.0-0.00.098.00.00.00.0101.00.00.00.0102.5103.40.0

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod

us-gaap:RestrictedStockUnitsRSU



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
Value000000000001000110011001122
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue

us-gaap:RestrictedStockUnitsRSU



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
Value141.01.0-1.0-4.0117.00.0-1.0-3.0101.00.00.0-8.090.00.00.0-3.073.00.00.0-1.059.00.00.0-2.051.046.043.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue100.0100.0100.0100.0100.00.0100.0100.0100.00.00.0100.0100.00.00.0100.0100.00.00.0100.0100.00.00.0100.0100.0100.0100.0

us-gaap:ShortTermDebtType

us-gaap:ShorttermDebtAverageOutstandingAmount

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value456-3065663932314820744125-57031836714271
Percentage of ShorttermDebtAverageOutstandingAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation

us-gaap:CommonStockIncludingAdditionalPaidInCapital



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value100100010011
Percentage of StockIssuedDuringPeriodSharesShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value-1129-47-96-810-41-109-421-53-85-21423-118-22017015-215-114162
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStockIncludingAdditionalPaidInCapital



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value-11210-47-96-911-41-109-321-53-85-21422018-22118015-215-114162
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0111.1100.0100.0112.5110.0100.0100.075.0100.0100.0100.0100.095.7-0.0100.0100.5105.90.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShareRepurchaseProgram

us-gaap:TreasuryStockAcquiredAverageCostPerShare

aon:ShareRepurchaseProgramOf2012



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-312017-12-312017-09-302017-07-312017-06-302017-03-312016-09-302016-06-302016-04-302016-03-312015-09-302015-06-302015-03-31
Value212.783.0700000000000216190.83183.23161.161.789999999999992145.71141.23140.94134.412.089999999999975139.61133.24128.54114.46110.260.0103.5897.9295.75100.92100.15
Percentage of TreasuryStockAcquiredAverageCostPerShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:ShareRepurchaseProgram, us-gaap:SubsequentEventType

aon:ShareRepurchaseProgramOf2012, us-gaap:SubsequentEvent



Period End2019-10-252018-10-262017-10-312017-07-312016-10-282016-04-29
Value193.91146.52146.52133.24112.0103.58
Percentage of TreasuryStockAcquiredAverageCostPerShare0.00.00.0100.00.00.0

us-gaap:ShareRepurchaseProgram

us-gaap:TreasuryStockSharesAcquired

aon:ShareRepurchaseProgramOf2012



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-312017-12-312017-09-302017-07-312017-06-302017-03-312016-12-312016-09-302016-06-302016-04-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value221501223093508179200766632
Percentage of TreasuryStockSharesAcquired100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:ShareRepurchaseProgram, us-gaap:SubsequentEventType

aon:ShareRepurchaseProgramOf2012, us-gaap:SubsequentEvent



Period End2019-10-252018-10-262017-10-312017-07-312016-10-282016-04-29
Value25000.0200000.0165000.0450000.0128000.0600000.0
Percentage of TreasuryStockSharesAcquired0.00.00.090.00.00.0

us-gaap:StatementEquityComponents

us-gaap:CommonStockIncludingAdditionalPaidInCapital



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value2150122335811207462255775
Percentage of TreasuryStockSharesAcquired100.0100.0100.0100.0100.0100.0100.0100.03.798.1101.2100.02.1100.00.0100.06.5100.096.7100.00.00.00.00.00.0

us-gaap:TreasuryStockValueAcquiredCostMethod



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
Value46335010561011983014025535027531034126206301075040060030025050050065060030010035050
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShareRepurchaseProgram

aon:ShareRepurchaseProgramOf2012



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312018-01-312017-12-312017-09-302017-07-312017-06-302017-03-312016-12-312016-09-302016-06-302016-04-302016-03-312015-12-312015-08-312015-09-302015-06-302015-03-31
Value4614503501050100197300400550157700749601000125610030106575047505000600300250
Percentage of TreasuryStockValueAcquiredCostMethod99.60.0100.099.499.099.599.799.599.50.01533.999.50.096.799.22961.2100.00.00.0100.01187.5100.00.0100.0100.0

us-gaap:ShareRepurchaseProgram, us-gaap:SubsequentEventType

aon:ShareRepurchaseProgramOf2012, us-gaap:SubsequentEvent



Period End2019-10-252018-10-262017-10-312017-07-312016-10-282016-04-29
Value42424601465
Percentage of TreasuryStockValueAcquiredCostMethod0.00.00.00.00.00.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value463350105610119830140255350275310341262063010750400600300250500500650600300
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

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

aon:BasisMoneyMarketFundsAndHighlyLiquidSecuritiesFairValueDisclosure

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring, aon:MoneyMarketFundsAndOtherHighlyLiquidDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value225220071851235619791759206317091847
Percentage of BasisMoneyMarketFundsAndHighlyLiquidSecuritiesFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument

us-gaap:FairValueMeasurementsRecurring, aon:MoneyMarketFundsAndOtherHighlyLiquidDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value225220071851235619791759206317091847
Percentage of BasisMoneyMarketFundsAndHighlyLiquidSecuritiesFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncomeTaxAuthority

aon:CapitalLossCarryforwards

aon:OtherCountry



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value29302322182062238665
Percentage of CapitalLossCarryforwards100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DomesticCountry



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value411400415294360380270251
Percentage of CapitalLossCarryforwards1417.21333.3178.9134.9174.8170.4314.0386.2

us-gaap:InternalRevenueServiceIRS



Period End2019-12-312018-12-312017-12-31
Value1123670
Percentage of CapitalLossCarryforwards386.21223.30.0

us-gaap:StateAndLocalJurisdiction



Period End2019-12-312018-12-312017-12-31
Value1232210
Percentage of CapitalLossCarryforwards424.1736.70.0

aon:CashandCashEquivalentsandShortTermInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-31
Value86092877981673482865166071512852389343063372194668910527407838517217685997261000
Percentage of CashandCashEquivalentsandShortTermInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aon:DeferredTaxAssetsAccruedInterest



Period End2019-12-312018-12-31
Value1160
Percentage of DeferredTaxAssetsAccruedInterest100.00.0

aon:DeferredTaxAssetsLeaseGuarantees



Period End2019-12-312018-12-312017-12-312016-12-31
Value3560
Percentage of DeferredTaxAssetsLeaseGuarantees100.0100.0100.00.0

aon:DeferredTaxAssetsNetOperatingAndCapitalLossCarryforwardsAndTaxCreditCarryforwards



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value440563362399349295354368484
Percentage of DeferredTaxAssetsNetOperatingAndCapitalLossCarryforwardsAndTaxCreditCarryforwards100.0100.0100.0100.0100.0100.0100.0100.0100.0

aon:DeferredTaxLiabilitiesIntangibleAssetsAndPropertyPlantAndEquipment



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value2513104369829611058107411281333
Percentage of DeferredTaxLiabilitiesIntangibleAssetsAndPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0

aon:DeferredTaxLiabilitiesOtherAccruedExpenses



Period End2019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value253612101994039621214132
Percentage of DeferredTaxLiabilitiesOtherAccruedExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanSponsorLocation, us-gaap:RetirementPlanType

aon:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationUnderlyingPriceInflation

country:GB, us-gaap:PensionPlansDefinedBenefit