MKTX


Line plots across dimensions of each concept
Tables

Table of contents



us-gaap:CommonStockValue

us-gaap:CommonStockSharesIssued
us-gaap:StatementClassOfStock

us-gaap:CommonStockSharesOutstanding
us-gaap:StatementClassOfStock

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:ProductOrService
us-gaap:ProductOrService, us-gaap:TimingOfTransferOfGoodOrService
us-gaap:StatementGeographical

us-gaap:Revenues

us-gaap:GeneralAndAdministrativeExpense

us-gaap:OperatingExpenses

us-gaap:GeneralAndAdministrativeExpense

us-gaap:OperatingIncomeLoss

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
us-gaap:StatementEquityComponents

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:NonoperatingIncomeExpense

us-gaap:IncomeTaxExpenseBenefit

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:NetIncomeLoss
us-gaap:StatementEquityComponents

us-gaap:Assets

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:PropertyPlantAndEquipmentNet
us-gaap:StatementGeographical

us-gaap:Goodwill
us-gaap:BusinessAcquisition

us-gaap:IntangibleAssetsNetExcludingGoodwill

us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FairValueByAssetClass
us-gaap:IntangibleAssetsNetIncludingGoodwill

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:CommonStockValue

us-gaap:AdditionalPaidInCapitalCommonStock

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:TreasuryStockValue

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:PaymentsForRepurchaseOfCommonStock

us-gaap:EffectiveIncomeTaxRateContinuingOperations
us-gaap:TitleOfIndividual, us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod

us-gaap:ShareBasedCompensation

us-gaap:OperatingLeaseRightOfUseAsset

mktx:AdjustmentsRelatedToTaxWithholdingExpenseBenefitForShareBasedCompensation
us-gaap:StatementEquityComponents

mktx:AmortizationOfOperatingLeaseRightOfUseAssets

mktx:ContractWithCustomerLiabilityForeignCurrencyTranslation
us-gaap:ProductOrService

mktx:ContractWithCustomerLiabilityPaymentsReceived
us-gaap:ProductOrService
us-gaap:ProductOrService
mktx:DisclosedTrading
us-gaap:ProductOrService
mktx:DistributionFeesAndUnusedMinimumFees

mktx:IncreaseDecreaseInOperatingLeaseLiabilities
us-gaap:IncomeStatementLocation
mktx:OperatingLeaseCostForSubleased

mktx:TransactionCosts
us-gaap:ProductOrService
mktx:VariableTransactionFees

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents

us-gaap:AllocatedShareBasedCompensationExpense
us-gaap:TitleOfIndividual

us-gaap:AmortizationOfIntangibleAssets
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationConsiderationTransferred1

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:CommunicationsAndInformationTechnology

us-gaap:ContractWithCustomerLiabilityRevenueRecognized
us-gaap:ProductOrService

us-gaap:CurrentFederalTaxExpenseBenefit

us-gaap:CurrentForeignTaxExpenseBenefit

us-gaap:CurrentIncomeTaxExpenseBenefit

us-gaap:CurrentStateAndLocalTaxExpenseBenefit

us-gaap:DeferredFederalIncomeTaxExpenseBenefit

us-gaap:DeferredForeignIncomeTaxExpenseBenefit

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:DeferredIncomeTaxesAndTaxCredits

us-gaap:DeferredStateAndLocalIncomeTaxExpenseBenefit

us-gaap:DepreciationAmortizationAndAccretionNet

us-gaap:DepreciationAndAmortization

us-gaap:DividendsCommonStockCash
us-gaap:StatementEquityComponents

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations

us-gaap:EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities

us-gaap:IncreaseDecreaseInAccountsReceivable

us-gaap:IncreaseDecreaseInContractWithCustomerLiability

us-gaap:IncreaseDecreaseInEmployeeRelatedLiabilities

us-gaap:IncreaseDecreaseInIncomeTaxes

us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets

us-gaap:IncreaseDecreaseInTradingSecurities
us-gaap:InvestmentType

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InvestmentIncomeNonoperating

us-gaap:LaborAndRelatedExpense

us-gaap:LeaseCost

us-gaap:MarketingAndAdvertisingExpense

us-gaap:NumberOfOperatingSegments

us-gaap:OccupancyNet
us-gaap:ProductOrService
us-gaap:OperatingLeaseCost

us-gaap:OtherComprehensiveIncomeForeignCurrencyTranslationGainLossArisingDuringPeriodTax

us-gaap:OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax

us-gaap:OtherNoncashIncomeExpense

us-gaap:PaymentsOfOrdinaryDividends

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt

us-gaap:PaymentsToDevelopSoftware
us-gaap:ProductOrService
us-gaap:PrincipalTransactionsRevenue
us-gaap:ProductOrService, us-gaap:FinancialInstrument

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities

us-gaap:ProceedsFromSaleAndMaturityOfMarketableSecurities

us-gaap:ProceedsFromStockOptionsExercised

us-gaap:ProfessionalFees
us-gaap:TitleOfIndividual, us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised
us-gaap:StatementEquityComponents

us-gaap:StockRepurchasedAndRetiredDuringPeriodValue
us-gaap:StatementEquityComponents
us-gaap:IncomeStatementLocation
us-gaap:SubleaseIncome
us-gaap:ProductOrService
us-gaap:VariableLeaseCost

mktx:MarketableSecuritiesAccumulatedGrossUnrealizedGainBeforeTax

mktx:MarketableSecuritiesAccumulatedGrossUnrealizedLossBeforeTax

mktx:MarketableSecuritiesAfterOneThroughFiveYearsFairValue

mktx:MarketableSecuritiesAmortizedCost

mktx:MarketableSecuritiesWithinOneYearFairValue

mktx:MoneyMarketFundsFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel

mktx:TradingSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:InvestmentType

mktx:TradingSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:InvestmentType

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent

us-gaap:AccountsReceivableNet

us-gaap:AllowanceForDoubtfulAccountsReceivable

us-gaap:AssetsFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:InvestmentType
us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:InvestmentType
us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:InvestmentType
us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:InvestmentType
us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:InvestmentType

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations

us-gaap:ContractWithCustomerLiability
us-gaap:ProductOrService
us-gaap:InvestmentType
us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months
us-gaap:InvestmentType
us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
us-gaap:InvestmentType
us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPosition
us-gaap:InvestmentType
us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss

us-gaap:DeferredIncomeTaxAssetsNet

us-gaap:DepositsAssets
us-gaap:SubsequentEventType
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeAssetNotionalAmount

us-gaap:DerivativeFairValueOfDerivativeNet
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeNotionalAmount

us-gaap:EmployeeRelatedLiabilitiesCurrentAndNoncurrent

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsGross
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:MarketableSecurities

us-gaap:OperatingLeaseLiability

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent

us-gaap:PrepaidExpenseAndOtherAssets

us-gaap:TaxesPayableCurrentAndNoncurrent

us-gaap:TradingSecuritiesDebt
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:InvestmentType
us-gaap:InvestmentType

us-gaap:TradingSecuritiesDebtAmortizedCost
us-gaap:InvestmentType

us-gaap:TreasuryStockShares

Tables

  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:CommonStockValue ▄▄▄▄122000.0122000.0122000.0122000.0NA122000.0NANANANANANANANANANANANANANANANANA119000.0119000.0119000.0NANANANANANANANANANANANANANA
us-gaap:CommonStockSharesIssued ████████████████▁▁▁▁▁▁▁▁▁▁4040404040404040404040404040404039393939393939393939NANANANANANANANANANANANANANA
us-gaap:CommonStockSharesOutstanding ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄3737373737373737373737373737373737373737373737373737NANANANANANANANANANANANANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding 38NA373737NA373737NA383838NA373737NA373737NA373738NA373737NA0038NA393939NA3839
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic 37NA373737NA363636NA363636NA363636NA363636NA363737NA363636NA0036NA373636NA3233
us-gaap:EarningsPerShareBasic █▆▆▅▆▅▄▅▅▄▄▄▅▄▃▄▃▃▃▃▃▃▂▂▂▃▂▂▂▂▂▂▂▁▂▂▁▁▁▁2.011.36000000000000031.461.31.421.23999999999999981.041.11.30.90999999999999970.931.031.150.89999999999999990.840.90.790.67000000000000020.620.660.670.58999999999999990.470.490.470.63000000000000010.490.520.420.56999999999999980.370.350.370.310000000000000050.360.320.30.250.240.19
us-gaap:EarningsPerShareDiluted █▅▆▅▆▅▄▄▅▄▄▄▅▄▄▄▃▃▃▃▃▃▂▂▂▃▂▂▂▂▂▂▂▁▂▁▁▁▁▁1.961.32000000000000031.421.271.391.21000000000000041.021.071.270.88000000000000030.91.01.110.87999999999999990.820.880.770.64999999999999990.60.640.650.57000000000000010.460.480.460.60999999999999990.480.510.410.540.360.340.350.28999999999999990.340.30.270.23000000000000010.220.18
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax █▆▆▆▆▅▄▅▅▄▄▄▅▄▄▄▄▃▃▃▃▃▃▃▂▂▂▃▂▂▂▂▂▂▂▂▁▁▁▁168129131125124112101106114989596103929096887674757670646463606165555048485045464543383735
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ProductOrService mktx:CommissionRevenue█▄▄▄▄▃▁▂▃▁▁▁1551171191141121019096102878687NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementGeographical country:GB█▇▇▇▇▅▄▅▅▄▄▄▄▄▃▄▃▂▁▁▂▁▁▁▁22212120201615161714141415141214121099109999NANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementGeographical country:US█▅▅▅▅▄▄▄▄▃▃▃▄▃▃▃▃▂▂▂▂▂▁▁▁1411071091041039585909683808187777782756664656660545553NANANANANANANANANANANANANANANA
us-gaap:Revenues █▆▆▆▆▅▄▅▅▄▄▄▅▄▄▄▄▃▃▃▃▃▃▃▂▂▂▃▂▂▂▂▂▂▂▂▁▁▁▁168129131125124112101106114999697103949096887674757670646463606165555048485045464543383735
us-gaap:GeneralAndAdministrativeExpense ▄█▄▄▄▄▃▃▃▄▄▃▃▄▄▆▄▄▄▄▃▃▃▃▃▃▁▃▃▃▃▃▃▄▁▁▁▃▁▁3533332223322334333322222212222223111211
us-gaap:OperatingExpenses █▆▆▆▅▅▄▄▄▄▃▃▃▂▂▃▂▂▂▂▂▁▁▁776865646158555454504947484443464439383838363535NANANANANANANANANANANANANANANANA
us-gaap:GeneralAndAdministrativeExpense ▄█▄▄▄▄▃▃▃▄▄▃▃▄▄▆▄▄▄▄▃▃▃▃▃▃▁▃▃▃▃▃▃▄▁▁▁▃▁▁3533332223322334333322222212222223111211
us-gaap:OperatingIncomeLoss █▃▄▃▄▂▁▂▃▁▁▁▂91606560635346526048464855NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherNonoperatingIncomeExpense ▂▂▁▆▇█▅▅▅▃▄▅▅-656000.0-661000.0-838000.0-64000.042000.0175000.0-250000.0-207000.0-328000.0-534000.0-382000.0-252000.0-298000.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax ▁█▄▄▇▅▅▄▅▅▇▇▅▄▄▄▂▅▅▅▅▅▅▅▅▅▅▅▅▅▅▅▅▅▅-32-1-1100-100110-1-1-1-2000000000000000000NANANANANA
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest █▅▆▅▅▄▄▄▅▄▄▄▄▄▄▄▃▂▂▃▃▂▂▂▂▁▂▂▁▁▁91616762655647536149474955504650443635373833282927242631242221NANANANANANANANANA
us-gaap:NonoperatingIncomeExpense ▁▄▄███▄▄▁▁▁▁▁0112221100000NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeTaxExpenseBenefit █▅▆▇▆▅▄▆▆▇▆▅▆█▇█▇▆▆▆▆▅▅▅▅▄▄▆▄▁▄▄▄▄▄▄▃▃▂▂16111314121091213151311131715171512121213111010109812817897876544
us-gaap:ComprehensiveIncomeNetOfTax █▆▆▅▆▅▄▄▅▄▄▄▅▃▃▃▃▃▂▃▃▂▂▂▂▂▂▂▁▂▁▁▁▁▁▁▁70525247544538394733353942312931262422232421171817221719142013121311131210NANANA
us-gaap:NetIncomeLoss █▅▆▅▆▅▄▄▅▄▄▄▅▄▃▄▃▃▃▃▃▂▂▂▂▃▂▂▂▂▂▂▂▁▂▁▁▁▁▁74505448524538404733343842333033282422242421171817231819152013121311131110887
 us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings74NA544852453840473334384233303328242224242117181723181915201312131113NANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:Assets ██▇▆▆▅▅▄▄▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▂▂▁975954855812774695646617589581562547530528502477451439416398378379362356346351332305282279304289274349339321NA299NANA
us-gaap:Liabilities ██▇▇▆▄▃▃▂▃▂▂▂▃▂▂▂▂▂▂▁▂▁▁▁▂▂▁▁▂▁▁▁▂▁▁17718416015014387676052665145486050404148423934453633284146343037322725373328NA34NANA
us-gaap:LiabilitiesAndStockholdersEquity ██▇▆▆▅▅▄▄▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▂▂▁975954855812774695646617589581562547530528502477451439416398378379362356346351332305282279304289274349339321NA299NANA
us-gaap:StockholdersEquity ██▇▆▆▆▅▅▅▄▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁▁▂▂▂797770694661631607578557537514510501482468451436410390373359344334326322318310286270252242271261248312305292NA234NANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital▇███▇█▇▇▆▇████▇▇▆▆▆▅▅▅▄▄▃▃▃▃▂▂▂▁▁█▇▇328342343341335341336331327331342343339342337333324321317313309307302298295295289286283283277275270340335332NA340NANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:RetainedEarnings█▇▇▇▆▆▆▆▅▅▅▄▄▄▄▃▃▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁6435915605254964634334103853533323102852552312101871681501351181018674625132194-5261780-8-18NA-34NANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:CashAndCashEquivalentsAtCarryingValue █▅▇▆▅▅▄▃▂▃▂▂▂▃▂▂▂▃▂▃▂▃▂▂▂▂▁▂▁▂▂▂▁▃▂▂▁▁▁▁363270320286260246210170156167138128137168161153137199160169161168155133130132119135125128150129119169157135116124108113
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:PropertyPlantAndEquipmentNet ██▇▇▇▇▆▅▄▄▄▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▁▁▁▁▁747166646163545039383534333130313230313131323234333227261818181414141413NA12NANA
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  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:StockholdersEquity ██▇▆▆▆▅▅▅▄▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁▁▂▂▂797770694661631607578557537514510501482468451436410390373359344334326322318310286270252242271261248312305292NA234NANA
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us-gaap:CommonStockValue ▄▄▄▄122000.0122000.0122000.0122000.0NA122000.0NANANANANANANANANANANANANANANANANA119000.0119000.0119000.0NANANANANANANANANANANANANANA
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us-gaap:RetainedEarningsAccumulatedDeficit █▇▇▇▆▆▆▆▅▅▅▄▄▄▄▃▃▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁6435915605254964634334103853533323102852552312101871681501351181018674625132194-5261780-8-18NA-34NANA
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▁▃▂▃▃▂▂▃▃▃▃▃▂▂▃▄▅▆▆▆▆▆▆▆▆▆▇▇▇▇▇▇▇███-14-10-12-11-10-12-12-11-10-10-10-11-12-12-10-9-7-5-4-4-4-4-4-4-4-4-3-3-3-3-2-2-2-1-1-1NA-1NANA
us-gaap:TreasuryStockValue ▇▆████▇▇▇▇▆▆▅▅▄▄▄▄▄▄▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁158153196193190184178172166159153141129117107989493908479705746353232323232292828251818NA70NANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:NetCashProvidedByUsedInOperatingActivities █▆▄▄▂▄▄▃▁▂▃12089676939706754314652NANA655228-5743353010NANANA10233719102827121318271812219NA
us-gaap:NetCashProvidedByUsedInInvestingActivities █▁▆▆▇▆▆▆▆▇▆24-106-4-2110-13-7-16-1214-13NANA-29-25-465-32-9-1NANANA0-8-48-6-51-10150-22-800NA
us-gaap:NetCashProvidedByUsedInFinancingActivities ▁▅▆█▄██▇▆▅▆-49822000.0-32041000.0-27527000.0-22305000.0-36227000.0-20242000.0-20551000.0-22435000.0-29445000.0-32733000.0-28880000.0NANA-27915000.0-17792000.0-8902000.0-10685000.0-10110000.0-12120000.0-11583000.0-17241000.0NANANA-11916000.0-1691000.0-3997000.0-3459000.0-7927000.0-50595000.0-5115000.0-1747000.0-78718000.0-6678000.0-2437000.0-1648000.0-436000.0-5938000.0-22766000.0NA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:NetCashProvidedByUsedInOperatingActivities █▆▄▄▂▄▄▃▁▂▃12089676939706754314652NANA655228-5743353010NANANA10233719102827121318271812219NA
us-gaap:NetIncomeLoss █▅▆▅▆▅▄▄▅▄▄▄▅▄▃▄▃▃▃▃▃▂▂▂▂▃▂▂▂▂▂▂▂▁▂▁▁▁▁▁74505448524538404733343842333033282422242421171817231819152013121311131110887
 us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings74NA544852453840473334384233303328242224242117181723181915201312131113NANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:NetCashProvidedByUsedInInvestingActivities █▁▆▆▇▆▆▆▆▇▆24-106-4-2110-13-7-16-1214-13NANA-29-25-465-32-9-1NANANA0-8-48-6-51-10150-22-800NA
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▃▃▂▄▁▇▅█▂▃▂▂▃▂▁▂▂▂▂▂▁▁▁▂▂▄▂▄▁▁▃▁▁▁▂▂▁▁▁43250127132411410121110002151600300011000NA
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us-gaap:NetCashProvidedByUsedInFinancingActivities ▁▅▆█▄██▇▆▅▆-49822000.0-32041000.0-27527000.0-22305000.0-36227000.0-20242000.0-20551000.0-22435000.0-29445000.0-32733000.0-28880000.0NANA-27915000.0-17792000.0-8902000.0-10685000.0-10110000.0-12120000.0-11583000.0-17241000.0NANANA-11916000.0-1691000.0-3997000.0-3459000.0-7927000.0-50595000.0-5115000.0-1747000.0-78718000.0-6678000.0-2437000.0-1648000.0-436000.0-5938000.0-22766000.0NA
us-gaap:PaymentsForRepurchaseOfCommonStock ▄▄▂▂▄▄▄▄▄▄█▇█▇▅▃▁▂▄▄▅█▇▇▂55235666661211121084135581211103NANANANA21NANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312014-06-302014-03-312013-12-31
Value122000.0122000.0122000.0122000.0122000.0119000.0119000.0119000.0
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.0

Common Stock Par Or Stated Value Per Share

Common Stock Shares Issued

us-gaap:CommonStockSharesIssued



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value4040404040404040404040404040404039393939393939393939
Percentage of CommonStockSharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementClassOfStock

us-gaap:NonvotingCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-312011-12-312011-09-302010-12-31
Value0000000000000000000000000222
Percentage of CommonStockSharesIssued0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value3737373737373737373737373737373737373737373737373737
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementClassOfStock

us-gaap:NonvotingCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-312012-09-302012-06-302011-12-312011-09-302010-12-31
Value000000000000000000000000022222
Percentage of CommonStockSharesOutstanding0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Shares Authorized

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value3837373737373738383837373737373737373837373700383939393839
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value3737373736363636363636363636363636373736363600363736363233
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value2.011.36000000000000031.461.31.421.23999999999999981.041.11.30.90999999999999970.931.031.150.89999999999999990.840.90.790.67000000000000020.620.660.670.58999999999999990.470.490.470.63000000000000010.490.520.420.56999999999999980.370.350.370.310000000000000050.360.320.30.250.240.19
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value1.961.32000000000000031.421.271.391.21000000000000041.021.071.270.88000000000000030.91.01.110.87999999999999990.820.880.770.64999999999999990.60.640.650.57000000000000010.460.480.460.60999999999999990.480.510.410.540.360.340.350.28999999999999990.340.30.270.23000000000000010.220.18
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Income Loss From Continuing Operations Per Basic Share

Income Loss From Continuing Operations Per Diluted Share

Revenue From Contract With Customer Excluding Assessed Tax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value168129131125124112101106114989596103929096887674757670646463606165555048485045464543383735
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

mktx:CommissionRevenue



Period 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
Value1551171191141121019096102878687
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax92.390.291.190.990.690.289.289.989.689.390.390.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax92.390.291.190.990.690.289.289.989.689.390.390.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:CommissionRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:InformationServices



Period 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
Value887777767666
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.16.65.85.75.96.37.16.56.26.96.66.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.16.65.85.75.96.37.16.56.26.96.66.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:InformationServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:OtherRevenues



Period 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
Value000000000000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.20.20.20.20.20.30.30.30.30.30.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.20.20.20.20.20.30.30.30.30.30.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:OtherRevenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:PostTradeServices



Period 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
Value433343334322
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.53.02.93.23.33.33.43.44.03.52.82.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.53.02.93.23.33.33.43.44.03.52.82.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:PostTradeServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService, us-gaap:TimingOfTransferOfGoodOrService

mktx:InformationServices, us-gaap:TransferredAtPointInTime



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value00000000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.50.30.40.10.10.20.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.50.30.40.10.10.20.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:InformationServices us-gaap:TransferredAtPointInTime100.0100.0100.0100.0100.0100.0100.0100.0

mktx:InformationServices, us-gaap:TransferredOverTime



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value78777676
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.66.35.55.65.86.16.96.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.66.35.55.65.86.16.96.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:InformationServices us-gaap:TransferredOverTime100.0100.0100.0100.0100.0100.0100.0100.0

mktx:PostTradeServices, us-gaap:TransferredAtPointInTime



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value0000000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.10.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.10.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:PostTradeServices us-gaap:TransferredAtPointInTime100.0100.0100.0100.0100.0100.0100.0

mktx:PostTradeServices, us-gaap:TransferredOverTime



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value43334333
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.53.02.93.13.33.23.43.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.53.02.93.13.33.23.43.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:PostTradeServices us-gaap:TransferredOverTime100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementGeographical

country:GB



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value22212120201615161714141415141214121099109999
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.316.716.316.516.314.615.715.115.515.014.914.815.215.913.814.514.313.413.212.213.113.714.314.915.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.316.716.316.516.314.615.715.115.515.014.914.815.215.913.814.514.313.413.212.213.113.714.314.915.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax country:GB100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

country:US



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value1411071091041039585909683808187777782756664656660545553
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax83.882.883.283.083.285.083.984.484.184.784.784.884.583.785.985.085.186.286.487.386.685.985.484.784.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax83.882.883.283.083.285.083.984.484.184.784.784.884.583.785.985.085.186.286.487.386.685.985.484.784.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:OtherGeographicArea



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value4000000000000000000000000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.90.50.50.50.50.40.40.50.40.30.40.40.40.30.30.50.60.40.40.50.30.40.30.30.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.90.50.50.50.50.40.40.50.40.30.40.40.40.30.30.50.60.40.40.50.30.40.30.30.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mktx:OtherGeographicArea100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Revenues

us-gaap:Revenues



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value168129131125124112101106114999697103949096887674757670646463606165555048485045464543383735
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0101.0101.2101.0100.0102.4100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Investment Income

Other Income

General And Administrative Expense

us-gaap:GeneralAndAdministrativeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3533332223322334333322222212222223111211
Percentage of GeneralAndAdministrativeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.93.92.93.02.53.02.72.52.23.73.53.02.64.24.14.34.44.64.84.33.53.64.03.63.54.13.23.24.74.84.34.14.27.53.74.02.35.64.95.2

Operating Expenses

us-gaap:OperatingExpenses



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value776865646158555454504947484443464439383838363535
Percentage of OperatingExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax46.153.149.951.549.252.054.251.447.550.951.849.646.547.848.747.749.951.752.350.949.852.356.055.3

Operating Costs And Expenses

General And Administrative Expense

us-gaap:GeneralAndAdministrativeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3533332223322334333322222212222223111211
Percentage of GeneralAndAdministrativeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.93.92.93.02.53.02.72.52.23.73.53.02.64.24.14.34.44.64.84.33.53.64.03.63.54.13.23.24.74.84.34.14.27.53.74.02.35.64.95.2

Operating Income Loss

us-gaap:OperatingIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value91606560635346526048464855
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax53.946.950.148.550.848.045.848.652.549.648.850.953.1

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-656000.0-661000.0-838000.0-64000.042000.0175000.0-250000.0-207000.0-328000.0-534000.0-382000.0-252000.0-298000.0
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.4-0.5-0.6-0.10.00.2-0.2-0.2-0.3-0.5-0.4-0.3-0.3

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

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value-32-1-1100-100110-1-1-1-2000000000000000000
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-2.31.9-1.1-0.90.9-0.4-0.6-1.20.20.21.21.4-0.4-2.1-1.2-1.9-2.5-0.1-0.1-0.4-0.10.1-0.2-0.2-0.4-0.3-0.6-0.10.2-0.2-0.7-0.3-0.3-0.3-0.4

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value-3-1-1100-100110-1-1-1-20000000000000
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.099.9100.0100.0100.0100.0100.0100.0100.099.0100.4100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-2.3-1.1-0.90.9-0.4-0.6-1.20.20.21.21.4-0.4-2.1-1.2-1.9-2.5-0.1-0.1-0.4-0.10.1-0.2-0.2-0.4-0.3-0.6-0.10.2-0.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations

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

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value91616762655647536149474955504650443635373833282927242631242221
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax54.347.751.250.152.449.947.149.753.250.149.451.553.554.651.352.350.148.347.749.150.247.744.044.743.741.043.247.944.444.044.6

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

Income Loss From Continuing Operations Before Income Taxes Domestic

Income Loss From Continuing Operations Before Income Taxes Foreign

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0112221100000
Percentage of NonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.91.01.61.61.91.41.10.70.50.60.60.4

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value16111314121091213151311131715171512121213111010109812817897876544
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax10.09.010.111.810.29.19.111.911.416.113.712.012.718.617.118.017.416.317.017.018.116.916.816.716.115.413.318.616.22.116.017.618.216.219.017.415.814.213.113.3

Income Taxes Paid Net

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value70525247544538394733353942312931262422232421171817221719142013121311131210
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax41.740.740.037.843.540.437.536.741.733.936.940.840.533.733.032.430.431.630.531.732.130.927.027.827.238.029.229.426.940.127.125.425.925.228.926.723.9

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value74505448524538404733343842333033282422242421171817231819152013121311131110887
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax44.338.741.038.342.240.838.037.941.834.035.739.540.936.034.334.332.732.030.632.132.030.827.228.027.638.329.829.527.640.627.925.926.625.628.926.124.723.223.020.3

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value74544852453840473334384233303328242224242117181723181915201312131113
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax44.341.038.342.240.838.037.941.834.035.739.540.936.034.334.332.732.030.632.132.030.827.228.027.638.329.829.527.640.627.925.926.625.628.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss Available To Common Stockholders Basic

Assets

us-gaap:Assets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value975954855812774695646617589581562547530528502477451439416398378379362356346351332305282279304289274349339321299
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value1771841601501438767605266514548605040414842393445363328414634303732272537332834
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets18.219.418.818.518.512.610.49.88.811.49.18.49.111.410.08.69.211.010.39.89.012.010.19.58.111.713.811.410.713.310.89.79.310.69.88.811.6

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value975954855812774695646617589581562547530528502477451439416398378379362356346351332305282279304289274349339321299
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value797770694661631607578557537514510501482468451436410390373359344334326322318310286270252242271261248312305292234216194
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets81.880.681.281.581.587.489.690.291.288.690.991.690.988.690.091.490.889.089.790.291.088.089.990.591.988.386.288.689.386.789.290.390.789.490.291.278.30.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-14-10-12-11-10-12-12-11-10-10-10-11-12-12-10-9-7-5-4-4-4-4-4-4-4-4-3-3-3-3-2-2-2-1-1-1-1-1-1
Percentage of StockholdersEquity-1.8-1.3-1.8-1.7-1.7-2.0-2.1-2.1-1.9-2.0-2.0-2.3-2.6-2.6-2.2-2.1-1.8-1.3-1.3-1.4-1.3-1.4-1.4-1.4-1.3-1.3-1.4-1.3-1.4-1.3-1.0-0.9-0.9-0.6-0.6-0.6-0.7-0.6-0.7
Percentage of Assets-1.5-1.1-1.5-1.4-1.4-1.8-1.9-1.9-1.7-1.8-1.8-2.1-2.4-2.3-2.0-1.9-1.6-1.2-1.2-1.2-1.2-1.2-1.3-1.2-1.2-1.2-1.2-1.2-1.2-1.1-0.9-0.8-0.8-0.5-0.5-0.5-0.60.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value328342343341335341336331327331342343339342337333324321317313309307302298295295289286283283277275270340335332340313305
Percentage of StockholdersEquity41.144.549.551.653.156.258.159.461.064.367.068.470.373.174.776.479.282.285.087.189.791.992.792.592.995.2101.1106.0112.1116.8102.1105.1108.7109.1109.6113.4145.3145.0157.1
Percentage of Assets33.635.940.242.043.349.252.053.655.657.060.862.763.964.867.269.971.973.276.378.681.780.883.383.785.384.187.193.9100.1101.391.194.998.697.598.8103.4113.70.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312012-03-312011-12-312011-06-302010-12-312009-12-312008-12-31
Value000000000000000000000000000000000
Percentage of StockholdersEquity0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.1
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value6435915605254964634334103853533323102852552312101871681501351181018674625132194-5261780-8-18-34-55-68
Percentage of StockholdersEquity80.676.880.679.478.776.274.973.671.868.765.162.059.154.551.348.345.643.040.437.734.530.526.423.119.616.411.47.22.0-2.39.86.63.5-0.2-2.8-6.4-14.8-25.6-35.4
Percentage of Assets65.961.965.564.764.166.667.066.565.560.859.156.853.748.346.244.141.438.336.334.031.426.823.720.918.014.59.96.41.8-2.08.76.03.2-0.2-2.6-5.8-11.60.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-158-153-196-193-190-184-178-172-166-159-153-141-129-117-107-98-94-93-90-84-79-70-57-46-35-32-32-32-32-32-29-28-28-25-18-18-70-40-40
Percentage of StockholdersEquity-19.9-19.9-28.3-29.3-30.1-30.4-30.9-31.0-30.9-31.0-30.1-28.2-26.9-25.1-23.8-22.7-23.1-23.9-24.2-23.5-23.0-21.0-17.7-14.2-11.2-10.4-11.3-11.9-12.8-13.3-10.9-10.8-11.4-8.3-6.2-6.5-29.9-18.5-20.6
Percentage of Assets-16.3-16.1-23.0-23.8-24.5-26.6-27.7-28.0-28.2-27.5-27.3-25.9-24.4-22.2-21.4-20.7-20.9-21.3-21.7-21.2-20.9-18.5-15.9-12.9-10.3-9.2-9.7-10.6-11.4-11.5-9.8-9.8-10.3-7.4-5.6-5.9-23.40.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-312008-12-31
Value363270320286260246210170156167138128137168161153137199160169161168155133130132119135125128150129119169157135116124108113103107
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets37.328.337.535.233.735.432.527.626.528.724.723.425.931.932.232.130.545.538.542.442.544.542.737.337.537.735.844.444.546.149.244.743.648.546.542.30.041.70.00.00.00.0

Property Plant And Equipment Gross

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value74716664616354503938353433313031323031313132323433322726181818141414141312
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.77.57.87.97.99.18.48.16.76.66.36.36.45.96.16.67.17.07.57.88.28.59.09.69.69.38.38.76.66.46.15.25.44.14.14.24.2

us-gaap:StatementGeographical

country:GB



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312013-12-31
Value12977778910109877888899898
Percentage of PropertyPlantAndEquipmentNet16.513.111.111.012.312.415.818.226.327.327.525.823.224.826.226.027.728.829.530.128.528.125.4
Percentage of Assets1.31.00.90.91.01.11.31.51.81.81.71.61.51.51.61.72.02.02.22.42.42.42.4
Percentage of Assets country:GB0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

country:US



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312013-12-31
Value6262595753554540292725252623222323212121222324
Percentage of PropertyPlantAndEquipmentNet83.586.988.989.087.787.684.281.873.672.672.574.276.875.173.774.072.371.170.569.871.471.874.6
Percentage of Assets6.46.56.97.06.97.97.16.65.04.84.64.74.94.44.54.95.15.05.35.55.96.16.9
Percentage of Assets country:US0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

mktx:OtherGeographicArea



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312013-12-31
Value00000000000000000000000
Percentage of PropertyPlantAndEquipmentNet0.00.00.00.10.00.00.00.00.10.10.10.10.10.10.10.10.10.10.10.10.10.10.1
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets mktx:OtherGeographicArea0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Goodwill

us-gaap:Goodwill



Period End2020-03-312019-12-312018-12-312012-12-312012-09-302012-06-302011-12-31
Value1471465931313131
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets15.115.48.611.410.411.09.1

us-gaap:BusinessAcquisition

mktx:LiquidityEdgeLLC



Period End2020-03-312019-11-01
Value8787
Percentage of Goodwill59.50.0
Percentage of Assets9.00.0
Percentage of Assets mktx:LiquidityEdgeLLC0.00.0

Intangible Assets Net Excluding Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill



Period End2020-03-312019-12-312018-12-31
Value60602
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0
Percentage of Assets6.26.40.4

Finite Lived Intangible Assets Net

us-gaap:FiniteLivedIntangibleAssetsNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value6060222233333333334445667788911121122
Percentage of FiniteLivedIntangibleAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.26.40.30.30.40.40.50.50.60.60.60.60.70.70.80.80.91.01.21.41.61.82.02.22.42.62.93.74.30.50.60.70.8

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CustomerRelationships



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value60602222333333333344444444445661111
Percentage of FiniteLivedIntangibleAssetsNet99.999.8100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.092.984.277.371.767.163.159.856.954.352.455.153.986.474.265.855.5
Percentage of Assets6.26.40.30.30.40.40.50.50.60.60.60.60.70.70.80.80.90.91.01.11.21.21.31.31.41.41.52.02.30.40.40.50.4
Percentage of Assets us-gaap:CustomerRelationships0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TradeNames



Period End2020-03-312019-12-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value000000000000000000
Percentage of FiniteLivedIntangibleAssetsNet0.10.20.40.81.21.51.72.02.12.32.42.52.42.41.52.73.54.5
Percentage of Assets0.00.00.00.00.00.00.00.00.00.10.10.10.10.10.00.00.00.0
Percentage of Assets us-gaap:TradeNames0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Intangible Assets Net Including Goodwill

us-gaap:FairValueByAssetClass

us-gaap:IntangibleAssetsNetIncludingGoodwill

us-gaap:IndefinitelivedIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-31
Value1471465959595959595959595959595959595959595959595959
Percentage of IntangibleAssetsNetIncludingGoodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets15.115.47.07.47.78.69.29.710.110.310.610.911.211.311.912.513.213.614.315.015.815.716.516.717.0
Percentage of Assets us-gaap:IndefinitelivedIntangibleAssets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Deferred Tax Assets Liabilities Net

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value797770694661631607578557537514510501482468451436410390373359344334326322318310286270252242271261248312305292234216194
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets81.880.681.281.581.587.489.690.291.288.690.991.690.988.690.091.490.889.089.790.291.088.089.990.591.988.386.288.689.386.789.290.390.789.490.291.278.30.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-14-10-12-11-10-12-12-11-10-10-10-11-12-12-10-9-7-5-4-4-4-4-4-4-4-4-3-3-3-3-2-2-2-1-1-1-1-1-1
Percentage of StockholdersEquity-1.8-1.3-1.8-1.7-1.7-2.0-2.1-2.1-1.9-2.0-2.0-2.3-2.6-2.6-2.2-2.1-1.8-1.3-1.3-1.4-1.3-1.4-1.4-1.4-1.3-1.3-1.4-1.3-1.4-1.3-1.0-0.9-0.9-0.6-0.6-0.6-0.7-0.6-0.7
Percentage of Assets-1.5-1.1-1.5-1.4-1.4-1.8-1.9-1.9-1.7-1.8-1.8-2.1-2.4-2.3-2.0-1.9-1.6-1.2-1.2-1.2-1.2-1.2-1.3-1.2-1.2-1.2-1.2-1.2-1.2-1.1-0.9-0.8-0.8-0.5-0.5-0.5-0.60.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value328342343341335341336331327331342343339342337333324321317313309307302298295295289286283283277275270340335332340313305
Percentage of StockholdersEquity41.144.549.551.653.156.258.159.461.064.367.068.470.373.174.776.479.282.285.087.189.791.992.792.592.995.2101.1106.0112.1116.8102.1105.1108.7109.1109.6113.4145.3145.0157.1
Percentage of Assets33.635.940.242.043.349.252.053.655.657.060.862.763.964.867.269.971.973.276.378.681.780.883.383.785.384.187.193.9100.1101.391.194.998.697.598.8103.4113.70.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312012-03-312011-12-312011-06-302010-12-312009-12-312008-12-31
Value000000000000000000000000000000000
Percentage of StockholdersEquity0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.1
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value6435915605254964634334103853533323102852552312101871681501351181018674625132194-5261780-8-18-34-55-68
Percentage of StockholdersEquity80.676.880.679.478.776.274.973.671.868.765.162.059.154.551.348.345.643.040.437.734.530.526.423.119.616.411.47.22.0-2.39.86.63.5-0.2-2.8-6.4-14.8-25.6-35.4
Percentage of Assets65.961.965.564.764.166.667.066.565.560.859.156.853.748.346.244.141.438.336.334.031.426.823.720.918.014.59.96.41.8-2.08.76.03.2-0.2-2.6-5.8-11.60.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-158-153-196-193-190-184-178-172-166-159-153-141-129-117-107-98-94-93-90-84-79-70-57-46-35-32-32-32-32-32-29-28-28-25-18-18-70-40-40
Percentage of StockholdersEquity-19.9-19.9-28.3-29.3-30.1-30.4-30.9-31.0-30.9-31.0-30.1-28.2-26.9-25.1-23.8-22.7-23.1-23.9-24.2-23.5-23.0-21.0-17.7-14.2-11.2-10.4-11.3-11.9-12.8-13.3-10.9-10.8-11.4-8.3-6.2-6.5-29.9-18.5-20.6
Percentage of Assets-16.3-16.1-23.0-23.8-24.5-26.6-27.7-28.0-28.2-27.5-27.3-25.9-24.4-22.2-21.4-20.7-20.9-21.3-21.7-21.2-20.9-18.5-15.9-12.9-10.3-9.2-9.7-10.6-11.4-11.5-9.8-9.8-10.3-7.4-5.6-5.9-23.40.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312014-06-302014-03-312013-12-31
Value122000.0122000.0122000.0122000.0122000.0119000.0119000.0119000.0
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.0

Additional Paid In Capital Common Stock

us-gaap:AdditionalPaidInCapitalCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value328342343341335341336331327331342343339342337333324321317313309307302298295295289286283283277275270340335332340
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets33.635.940.242.043.349.252.053.655.657.060.862.763.964.867.269.971.973.276.378.681.780.883.383.785.384.187.193.9100.1101.391.194.998.697.598.8103.4113.7

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value6435915605254964634334103853533323102852552312101871681501351181018674625132194-5261780-8-18-34
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets65.961.965.564.764.166.667.066.565.560.859.156.853.748.346.244.141.438.336.334.031.426.823.720.918.014.59.96.41.8-2.08.76.03.2-0.2-2.6-5.8-11.6

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value-14-10-12-11-10-12-12-11-10-10-10-11-12-12-10-9-7-5-4-4-4-4-4-4-4-4-3-3-3-3-2-2-2-1-1-1-1
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-1.5-1.1-1.5-1.4-1.4-1.8-1.9-1.9-1.7-1.8-1.8-2.1-2.4-2.3-2.0-1.9-1.6-1.2-1.2-1.2-1.2-1.2-1.3-1.2-1.2-1.2-1.2-1.2-1.2-1.1-0.9-0.8-0.8-0.5-0.5-0.5-0.6

Treasury Stock Value

us-gaap:TreasuryStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value15815319619319018417817216615915314112911710798949390847970574635323232323229282825181870
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets16.316.123.023.824.526.627.728.028.227.527.325.924.422.221.420.720.921.321.721.220.918.515.912.910.39.29.710.611.411.59.89.810.37.45.65.923.4

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value12089676939706754314652655228-574335301010233719102827121318271812219
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax71.268.751.455.631.662.367.050.827.447.154.971.358.329.7-64.857.248.240.513.116.039.060.730.518.556.256.725.626.441.458.840.12.458.450.9

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value24-106-4-2110-13-7-16-1214-13-29-25-465-32-9-10-8-48-6-51-10150-22-800
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax14.5-82.3-3.5-17.08.5-11.8-7.5-15.6-11.114.5-14.2-31.7-28.7-4.57.27.3-43.9-13.1-1.4-0.7-14.1-78.8-10.4-10.02.4-2.5-1.831.30.5-6.05.8-19.9-0.0-2.6

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-49822000.0-32041000.0-27527000.0-22305000.0-36227000.0-20242000.0-20551000.0-22435000.0-29445000.0-32733000.0-28880000.0-27915000.0-17792000.0-8902000.0-10685000.0-10110000.0-12120000.0-11583000.0-17241000.0-11916000.0-1691000.0-3997000.0-3459000.0-7927000.0-50595000.0-5115000.0-1747000.0-78718000.0-6678000.0-2437000.0-1648000.0-436000.0-5938000.0-22766000.0
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-29.5-24.7-20.9-17.8-29.1-18.0-20.3-21.0-25.7-33.2-30.2-30.3-19.7-9.2-12.1-13.2-16.3-15.3-22.5-18.8-2.8-6.5-5.3-14.3-100.4-10.6-3.6-155.2-14.8-5.2-3.6-1.0-15.4-60.9

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value12089676939706754314652655228-574335301010233719102827121318271812219
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax71.268.751.455.631.662.367.050.827.447.154.971.358.329.7-64.857.248.240.513.116.039.060.730.518.556.256.725.626.441.458.840.12.458.450.9

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value74505448524538404733343842333033282422242421171817231819152013121311131110887
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax44.338.741.038.342.240.838.037.941.834.035.739.540.936.034.334.332.732.030.632.132.030.827.228.027.638.329.829.527.640.627.925.926.625.628.926.124.723.223.020.3

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value74544852453840473334384233303328242224242117181723181915201312131113
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax44.341.038.342.240.838.037.941.834.035.739.540.936.034.334.332.732.030.632.132.030.827.228.027.638.329.829.527.640.627.925.926.625.628.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Increase Decrease In Other Operating Capital Net

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value24-106-4-2110-13-7-16-1214-13-29-25-465-32-9-10-8-48-6-51-10150-22-800
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax14.5-82.3-3.5-17.08.5-11.8-7.5-15.6-11.114.5-14.2-31.7-28.7-4.57.27.3-43.9-13.1-1.4-0.7-14.1-78.8-10.4-10.02.4-2.5-1.831.30.5-6.05.8-19.9-0.0-2.6

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value43250127132411410121110002151600300011000
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-49822000.0-32041000.0-27527000.0-22305000.0-36227000.0-20242000.0-20551000.0-22435000.0-29445000.0-32733000.0-28880000.0-27915000.0-17792000.0-8902000.0-10685000.0-10110000.0-12120000.0-11583000.0-17241000.0-11916000.0-1691000.0-3997000.0-3459000.0-7927000.0-50595000.0-5115000.0-1747000.0-78718000.0-6678000.0-2437000.0-1648000.0-436000.0-5938000.0-22766000.0
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-29.5-24.7-20.9-17.8-29.1-18.0-20.3-21.0-25.7-33.2-30.2-30.3-19.7-9.2-12.1-13.2-16.3-15.3-22.5-18.8-2.8-6.5-5.3-14.3-100.4-10.6-3.6-155.2-14.8-5.2-3.6-1.0-15.4-60.9

Payments For Repurchase Of Common Stock

us-gaap:PaymentsForRepurchaseOfCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312012-12-312012-09-30
Value5523566666121112108413558121110321
Percentage of PaymentsForRepurchaseOfCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations



Period End2020-03-312019-03-31
Value0.1840.195
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0

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:TitleOfIndividual, us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod

mktx:EmployeeCompensationPlan, us-gaap:PerformanceShares



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value13295.00.03491.013225.00.00.010479.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod100.00.0100.0100.00.00.0100.0

mktx:EmployeeCompensationPlan, us-gaap:RestrictedStock



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value33359.09682.05139.082423.06716.090.046455.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod250.90.0147.2623.20.00.0443.3

Share Based Compensation

us-gaap:ShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value667554333333333333323222222212221110222
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Net

Unrecognized Tax Benefits

Deferred Tax Assets Valuation Allowance

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
Value7981757678
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0

Cash And Cash Equivalents Period Increase Decrease

mktx:AdjustmentsRelatedToTaxWithholdingExpenseBenefitForShareBasedCompensation



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value21601115007
Percentage of AdjustmentsRelatedToTaxWithholdingExpenseBenefitForShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value21601115007
Percentage of AdjustmentsRelatedToTaxWithholdingExpenseBenefitForShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0

mktx:AmortizationOfOperatingLeaseRightOfUseAssets



Period End2020-03-312019-03-31
Value11
Percentage of AmortizationOfOperatingLeaseRightOfUseAssets100.0100.0

mktx:ContractWithCustomerLiabilityForeignCurrencyTranslation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value88000.0-59000.027000.023000.0-20000.019000.012000.0
Percentage of ContractWithCustomerLiabilityForeignCurrencyTranslation100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

mktx:PostTradeServices



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value88000.0-59000.027000.023000.0-20000.019000.012000.0
Percentage of ContractWithCustomerLiabilityForeignCurrencyTranslation100.0100.0100.0100.0100.0100.0100.0

mktx:ContractWithCustomerLiabilityPaymentsReceived



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value6545534
Percentage of ContractWithCustomerLiabilityPaymentsReceived100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

mktx:InformationServices



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value2122111
Percentage of ContractWithCustomerLiabilityPaymentsReceived34.425.741.940.434.537.940.7

mktx:PostTradeServices



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value4423322
Percentage of ContractWithCustomerLiabilityPaymentsReceived65.674.358.159.665.562.159.3

us-gaap:ProductOrService

mktx:DisclosedTrading

mktx:CommissionRevenue



Period 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
Value846469676655495666545459
Percentage of DisclosedTrading100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

mktx:DistributionFeesAndUnusedMinimumFees

mktx:CommissionRevenue



Period 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
Value262523232324242422222016
Percentage of DistributionFeesAndUnusedMinimumFees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:IncreaseDecreaseInOperatingLeaseLiabilities



Period End2020-03-312019-03-31
Value-10
Percentage of IncreaseDecreaseInOperatingLeaseLiabilities100.0100.0

us-gaap:IncomeStatementLocation

mktx:OperatingLeaseCostForSubleased

mktx:OtherNet



Period End2020-03-312019-09-302019-06-302019-03-31
Value0000
Percentage of OperatingLeaseCostForSubleased100.0100.0100.0100.0

mktx:TransactionCosts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value53222212111111111
Percentage of TransactionCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

mktx:VariableTransactionFees

mktx:CommissionRevenue



Period 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
Value1299195908976657179656570
Percentage of VariableTransactionFees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value6755433333333333332322222221222111
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value6755433333333333332322222221222111
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllocatedShareBasedCompensationExpense



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value67553333333333332222212221110
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TitleOfIndividual

mktx:EmployeeCompensationPlan



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value65754433333333333322222222221111
Percentage of AllocatedShareBasedCompensationExpense95.80.097.095.294.60.092.593.093.40.093.293.493.80.091.695.893.80.091.095.192.20.088.293.590.20.091.895.192.489.391.395.2

mktx:NonEmployeeDirectorCompensationPlan



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value0240001500013000130001100090008000
Percentage of AllocatedShareBasedCompensationExpense4.20.03.04.85.40.07.57.06.60.06.86.66.20.08.44.26.20.09.04.97.80.011.86.59.80.08.24.97.6

us-gaap:AmortizationOfIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value0000000000000000000000000000000000
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

mktx:StockOptionsAndRestrictedStock



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
Value62964.05646.0232043.0346327.028760.019984.077732.010729.050817.059910.06480.091308.0238224.0130112.0131329.0249846.0
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationConsiderationTransferred1

mktx:LiquidityEdgeLLC



Period End2020-03-312019-11-01
Value153152
Percentage of BusinessCombinationConsiderationTransferred1100.0100.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value91-47342514363914-10
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommonStockDividendsPerShareDeclared



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value0.60.510.510.510.510.420.420.420.420.330.330.330.330.330.260.260.260.260.20.20.20.20.160.160.160.160.130.130.130.131.410.110.110.110.089999999999999970.090.090.090.070000000000000030.070.07
Percentage of CommonStockDividendsPerShareDeclared100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommunicationsAndInformationTechnology



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value8776565555544444433344444444333322222222
Percentage of CommunicationsAndInformationTechnology100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiabilityRevenueRecognized



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value5544444
Percentage of ContractWithCustomerLiabilityRevenueRecognized100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

mktx:InformationServices



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value1111111
Percentage of ContractWithCustomerLiabilityRevenueRecognized33.031.537.737.636.339.638.3

mktx:PostTradeServices



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value3333322
Percentage of ContractWithCustomerLiabilityRevenueRecognized67.068.562.362.463.760.461.7

us-gaap:CurrentFederalTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value7299686877119814131071011979984669356-2330
Percentage of CurrentFederalTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CurrentForeignTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value333322221311111111110000000000000000
Percentage of CurrentForeignTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CurrentIncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value1491415101110131191411111816149131412912111057811468-24312
Percentage of CurrentIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CurrentStateAndLocalTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value221110121011121111211211111110001011
Percentage of CurrentStateAndLocalTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredFederalIncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value12-101-10006001-1024-1-10300131003-3093464
Percentage of DeferredFederalIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredForeignIncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value000000001000000000000000000000000000
Percentage of DeferredForeignIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredIncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value22-102-1-1026-1010-135-1-101-10020-102-2002145443
Percentage of DeferredIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredIncomeTaxesAndTaxCredits



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value22-102-1-1026-101-1-1-220-1040004100
Percentage of DeferredIncomeTaxesAndTaxCredits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredStateAndLocalIncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value00000000000000000000000000000-1020001
Percentage of DeferredStateAndLocalIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DepreciationAmortizationAndAccretionNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value876665655544444444444444433322
Percentage of DepreciationAmortizationAndAccretionNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DepreciationAndAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value8766656555444444444444444334222111111111
Percentage of DepreciationAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DividendsCommonStockCash



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value22191919151515151212121299997777556644445244433
Percentage of DividendsCommonStockCash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value22191919151515151212121299997777556644445244433
Percentage of DividendsCommonStockCash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-32-1000000
Percentage of EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value6303101355
Percentage of EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value150-12-390501-2-1100-24-10000-504-54-14-10-22000000
Percentage of IncreaseDecreaseInAccountsPayableAndAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccountsReceivable



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value31-126-413-40-514-107-16-6-61012-82012-3-414-3-261-200-25-244-13
Percentage of IncreaseDecreaseInAccountsReceivable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInContractWithCustomerLiability



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value000000000
Percentage of IncreaseDecreaseInContractWithCustomerLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInEmployeeRelatedLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-251289-22778-20579-20689-18667-16656-17476-14444-13335-1145
Percentage of IncreaseDecreaseInEmployeeRelatedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInIncomeTaxes



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value130-5230-5490-10741-760-2-232-2030
Percentage of IncreaseDecreaseInIncomeTaxes100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-88-35-53-2302-4720-1032-550-2-22-100200-56-1-223000
Percentage of IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInTradingSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-56-49-2-65-96-3
Percentage of IncreaseDecreaseInTradingSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

mktx:MutualFundsHeldInRabbiTrust



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value00001000100010001
Percentage of IncreaseDecreaseInTradingSecurities-0.5-7.90.3-6.9-25.7-6.6-1.10.7-38.00.00.00.00.00.00.00.00.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value000000000011100000000000001001001200
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentIncomeNonoperating



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1122111111000
Percentage of InvestmentIncomeNonoperating100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LaborAndRelatedExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value41333232322726262824252527222325242121202119181818161715161414151513131516131414
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:LeaseCost



Period End2020-03-312019-09-302019-06-302019-03-31
Value3222
Percentage of LeaseCost100.0100.0100.0100.0

us-gaap:MarketingAndAdvertisingExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value2323232323221321111111111111011111110100
Percentage of MarketingAndAdvertisingExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:NumberOfOperatingSegments



Period End2020-03-312019-12-312019-09-30
Value1.00.00.0
Percentage of NumberOfOperatingSegments100.00.00.0

us-gaap:OccupancyNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3322233331111111111101111211000000000000
Percentage of OccupancyNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

us-gaap:OperatingLeaseCost

us-gaap:Occupancy



Period End2020-03-312019-09-302019-06-302019-03-31
Value3222
Percentage of OperatingLeaseCost100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeForeignCurrencyTranslationGainLossArisingDuringPeriodTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value2-2100001000-10002200000000000000
Percentage of OtherComprehensiveIncomeForeignCurrencyTranslationGainLossArisingDuringPeriodTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-491000.070000.0459000.0459000.0115000.072000.057000.0-334000.0-251000.027000.0-33000.023000.0-139000.0-44000.034000.0187000.0-168000.0-6000.0-69000.063000.0-50000.0-39000.04000.030000.044000.018000.0-9000.0-506000.0-164000.0-44000.0
Percentage of OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value-491000.070000.0459000.0459000.0115000.072000.057000.0-334000.0-251000.027000.0-33000.023000.0-139000.0-44000.034000.0187000.0-168000.0-6000.0-69000.063000.0-50000.0-39000.04000.030000.044000.0
Percentage of OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value-491000.08000.070000.0459000.0459000.0115000.072000.057000.0-334000.0-251000.026000.0-33000.023000.0-139000.0-44000.034000.0187000.0-168000.0-6000.0-69000.063000.0-46000.0-27000.04000.052000.044000.018000.0-9000.0-506000.0-164000.0-44000.0-56000.0-199000.0-65000.0186000.0392000.0-110000.0
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-155000.03000.022000.0144000.0143000.043000.023000.018000.0-107000.0-49000.016000.0-20000.014000.0-85000.0-27000.021000.0115000.0-104000.0-4000.0-43000.039000.0-25000.0-16000.02000.032000.028000.011000.0-5000.0-19000.0-70000.0-40000.0
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncashIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value-2036000.01672000.0-1182000.0-291000.0587000.0-333000.0-991000.0-1200000.0186000.0-663000.0-550000.0-347000.0-393000.0-292000.0-232000.0-317000.0-329000.0-411000.0-437000.0-772000.0-429000.0-243000.0-630000.0-294000.0-558000.0-381000.0-267000.0677000.0267000.0-447000.0
Percentage of OtherNoncashIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsOfOrdinaryDividends



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value23181818191515151512121212999977775556444551444333322
Percentage of PaymentsOfOrdinaryDividends100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value21760110007144070005000400040005001450004
Percentage of PaymentsRelatedToTaxWithholdingForShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.00.00.0100.0100.00.0100.0100.0100.0

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value8112174537610110157
Percentage of PaymentsToAcquireAvailableForSaleSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToDevelopSoftware



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value686432223333332333222222222111111110000
Percentage of PaymentsToDevelopSoftware100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

us-gaap:PrincipalTransactionsRevenue

mktx:CommissionRevenue



Period 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
Value402526232320161513111111
Percentage of PrincipalTransactionsRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService, us-gaap:FinancialInstrument

mktx:CommissionRevenue, us-gaap:USTreasurySecurities



Period End2020-03-31
Value4
Percentage of PrincipalTransactionsRevenue11.3

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value4514256367771031015141445446141281210941048131522243761054926
Percentage of ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleAndMaturityOfMarketableSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value111236275100101123117674953605621181613109410
Percentage of ProceedsFromSaleAndMaturityOfMarketableSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromStockOptionsExercised



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value0000011000000001000001000100020501-114
Percentage of ProceedsFromStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProfessionalFees



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value5676555555544444333333333444443232222221
Percentage of ProfessionalFees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TitleOfIndividual, us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

mktx:EmployeeCompensationPlan, us-gaap:PerformanceShares



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value360.90.015.289999999999992208.840.00.0202.04
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue100.00.0100.0100.00.00.0100.0

mktx:EmployeeCompensationPlan, us-gaap:RestrictedStock



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value367.229.45000000000001719.669999999999987213.62-2.1799999999999784-0.030000000000001137203.7
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue101.80.0128.6102.30.00.0100.8

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value000011000000001000001000100020501-1
Percentage of StockIssuedDuringPeriodValueStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value000011000000001000001000100020501-1
Percentage of StockIssuedDuringPeriodValueStockOptionsExercised100.0100.0100.0100.099.9100.0100.0100.0100.0100.0100.099.8100.0100.0100.0100.099.7100.0100.0100.0100.099.8100.0100.0100.0100.0100.099.8100.0100.099.9100.099.9100.0

us-gaap:StockRepurchasedAndRetiredDuringPeriodValue



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312012-12-312012-09-302012-06-302012-03-31
Value523566666121112108413558121110321071
Percentage of StockRepurchasedAndRetiredDuringPeriodValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:TreasuryStock



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312012-12-312012-09-302012-06-302012-03-31
Value523566666121112108413558121110321018
Percentage of StockRepurchasedAndRetiredDuringPeriodValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.025.6

us-gaap:IncomeStatementLocation

us-gaap:SubleaseIncome

mktx:OtherNet



Period End2020-03-312019-09-302019-06-302019-03-31
Value0000
Percentage of SubleaseIncome100.0100.0100.0100.0

us-gaap:ProductOrService

us-gaap:VariableLeaseCost

us-gaap:Occupancy



Period End2020-03-312019-09-302019-06-302019-03-31
Value16000.09000.031000.0124000.0
Percentage of VariableLeaseCost100.0100.0100.0100.0

mktx:MarketableSecuritiesAccumulatedGrossUnrealizedGainBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value02210000000000
Percentage of MarketableSecuritiesAccumulatedGrossUnrealizedGainBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:MarketableSecuritiesAccumulatedGrossUnrealizedLossBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value10000111100000
Percentage of MarketableSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:MarketableSecuritiesAfterOneThroughFiveYearsFairValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value5710911910493105959610910810498877671788047
Percentage of MarketableSecuritiesAfterOneThroughFiveYearsFairValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:MarketableSecuritiesAmortizedCost



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value136228233230221241237251245239237237218194
Percentage of MarketableSecuritiesAmortizedCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:MarketableSecuritiesWithinOneYearFairValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value7712011612712913414015313513013313813111799686637
Percentage of MarketableSecuritiesWithinOneYearFairValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:MoneyMarketFundsFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value1529916310815511211210161882511265837363161514651628080909073899983125106111
Percentage of MoneyMarketFundsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value1529916310815511211210161882511265837363161514651628080909073899983125106111
Percentage of MoneyMarketFundsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mktx:TradingSecuritiesAccumulatedGrossUnrealizedGainBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value01110000000000000
Percentage of TradingSecuritiesAccumulatedGrossUnrealizedGainBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

mktx:MutualFundsHeldInRabbiTrust



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value0100000000000
Percentage of TradingSecuritiesAccumulatedGrossUnrealizedGainBeforeTax25.064.253.052.851.193.683.173.863.271.046.128.635.5

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value00000000000000000
Percentage of TradingSecuritiesAccumulatedGrossUnrealizedGainBeforeTax75.00.92.30.60.33.4100.0100.0100.06.416.926.236.829.053.971.464.5

mktx:TradingSecuritiesAccumulatedGrossUnrealizedLossBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value10000000000000000
Percentage of TradingSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

mktx:MutualFundsHeldInRabbiTrust



Period End2020-03-312018-12-312018-09-302018-06-302018-03-31
Value10000
Percentage of TradingSecuritiesAccumulatedGrossUnrealizedLossBeforeTax87.037.0-35.8-3.82.7

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value00000000000000000
Percentage of TradingSecuritiesAccumulatedGrossUnrealizedLossBeforeTax13.0100.0100.0100.0100.063.0135.8103.897.3100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value34191617132919201414121416151515161213131211111819142012
Percentage of AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsReceivableNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value93627266705762616752635556505662524049464633364039343641353133333336313425
Percentage of AccountsReceivableNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllowanceForDoubtfulAccountsReceivable



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-312011-09-302011-06-302010-12-31
Value000000000000000000000000000000001000
Percentage of AllowanceForDoubtfulAccountsReceivable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetsFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value281327399339379351350351305327263246244252208188178146146113114127137145154157131104116134179164189
Percentage of AssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value1529916310815511211210161882511265837363161514651628080909073899983125106111
Percentage of AssetsFairValueDisclosure54.430.541.031.941.032.032.229.020.027.19.64.510.923.218.019.618.042.134.840.745.548.958.555.159.057.455.885.985.662.069.964.558.7

us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value12822723523022323923724924423823723521719417015114685956762645765636758141651545878
Percentage of AssetsFairValueDisclosure45.669.559.068.159.068.067.871.080.072.990.495.589.176.882.080.482.057.965.259.354.551.141.544.941.042.644.214.114.438.030.135.541.3

us-gaap:InvestmentType

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value373000.0721000.0732000.0681000.0238000.027000.09000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value303000.05000.024000.067000.0226000.0617000.0483000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value100137140144133147145
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:InvestmentType

us-gaap:AvailableForSaleSecuritiesDebtSecurities

us-gaap:FairValueInputsLevel2, us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312017-12-31
Value100137140145146145
Percentage of AvailableForSaleSecuritiesDebtSecurities100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value100137140145133146145
Percentage of AvailableForSaleSecuritiesDebtSecurities100.0100.0100.0100.00.0100.0100.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-31
Value365274321287262247211170157168169200
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiability



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value333332332
Percentage of ContractWithCustomerLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

mktx:InformationServices



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value222221221
Percentage of ContractWithCustomerLiability60.761.168.462.259.769.763.461.366.3

mktx:PostTradeServices



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value111110110
Percentage of ContractWithCustomerLiability39.338.931.637.840.330.336.638.733.7

us-gaap:InvestmentType

us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value512721142780177
Percentage of DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value479000.018000.019000.014000.018000.0256000.0536000.0
Percentage of DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPosition

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value51323869109167203
Percentage of DebtSecuritiesAvailableForSaleUnrealizedLossPosition100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value0000010
Percentage of DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredIncomeTaxAssetsNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302014-12-31
Value003113210187687659866
Percentage of DeferredIncomeTaxAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DepositsAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value241111111111111111
Percentage of DepositsAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:SubsequentEventType

us-gaap:SubsequentEvent



Period End2020-04-30
Value20
Percentage of DepositsAssets0.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeAssetNotionalAmount

us-gaap:ForeignExchangeContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value1641581341261221079989878588796967595251454238333130353329282715
Percentage of DerivativeAssetNotionalAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeFairValueOfDerivativeNet



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value-7-200-1
Percentage of DerivativeFairValueOfDerivativeNet100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk

us-gaap:ForeignExchangeContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302013-12-31
Value-7-2001-110000-2-1005-10000000
Percentage of DerivativeFairValueOfDerivativeNet100.0100.0100.0100.00.0100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:ForeignExchangeContract, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-31
Value-7-2001-110000-20
Percentage of DerivativeFairValueOfDerivativeNet100.0100.0100.0100.00.0100.00.00.00.00.00.00.00.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeNotionalAmount

us-gaap:ForeignExchangeContract



Period End2020-03-312019-12-312019-09-302018-12-31
Value156155134106
Percentage of DerivativeNotionalAmount100.0100.0100.0100.0

us-gaap:EmployeeRelatedLiabilitiesCurrentAndNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value2147352616393123153631231334282010292216825181262319125191510519151117
Percentage of EmployeeRelatedLiabilitiesCurrentAndNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value1099999998888888887766544332988776
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CustomerRelationships



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value432222222222111111111111000222221
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization38.634.631.230.529.829.128.427.626.926.125.324.423.422.521.720.920.120.020.320.820.921.522.223.224.025.224.729.829.529.429.529.730.2

us-gaap:NoncompeteAgreements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value000000000000000000000000000111110
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization3.63.84.04.04.14.14.24.24.34.34.44.44.54.54.64.64.74.64.54.54.44.24.13.93.63.32.914.115.015.115.014.814.5

us-gaap:TechnologyBasedIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-31
Value5555555555555555555443322
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization54.157.860.961.562.162.863.464.164.665.466.166.967.868.669.370.070.770.870.570.270.169.669.168.366.8

us-gaap:TradeNames



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value000000000000000000000000000000000
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization3.83.93.93.94.04.04.14.14.14.24.24.34.34.44.44.54.54.64.64.64.64.64.64.64.74.75.06.87.17.17.17.17.0

us-gaap:FiniteLivedIntangibleAssetsGross



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value70701212121212121212121212121212121212121212121212121220209999
Percentage of FiniteLivedIntangibleAssetsGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CustomerRelationships



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value64645555555555555555555555555883333
Percentage of FiniteLivedIntangibleAssetsGross90.690.646.346.446.446.446.446.446.446.446.446.446.346.346.446.446.546.546.546.646.546.646.646.746.646.646.643.843.837.637.637.637.6

us-gaap:NoncompeteAgreements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value000000000000000000000000000111111
Percentage of FiniteLivedIntangibleAssetsGross0.50.53.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.18.08.013.413.413.413.4

us-gaap:TradeNames



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value000000000000000000000000000000000
Percentage of FiniteLivedIntangibleAssetsGross0.70.73.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.03.04.34.36.36.36.36.3

us-gaap:MarketableSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value13523023523122224023624924423923723721819484
Percentage of MarketableSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingLeaseLiability



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value9697928990
Percentage of OperatingLeaseLiability100.0100.0100.0100.0100.0

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent



Period End2020-03-312019-03-31
Value0.0590.06
Percentage of OperatingLeaseWeightedAverageDiscountRatePercent100.0100.0

us-gaap:PrepaidExpenseAndOtherAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value20301822172218211718162113111113129712768129101011888136810127
Percentage of PrepaidExpenseAndOtherAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TaxesPayableCurrentAndNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302013-12-31
Value201613121816121218134415733104479533
Percentage of TaxesPayableCurrentAndNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TradingSecuritiesDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value34929486899394
Percentage of TradingSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:InvestmentType

us-gaap:FairValueInputsLevel2, mktx:MutualFundsHeldInRabbiTrust



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312017-12-31
Value665543
Percentage of TradingSecuritiesDebt18.76.76.26.84.43.4

us-gaap:FairValueInputsLevel2, us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312017-12-31
Value283133537191
Percentage of TradingSecuritiesDebt81.333.635.561.477.296.6

us-gaap:InvestmentType

mktx:MutualFundsHeldInRabbiTrust



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value6655543
Percentage of TradingSecuritiesDebt18.76.76.26.86.34.43.4

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value28313353567191
Percentage of TradingSecuritiesDebt81.333.635.561.463.277.296.6

us-gaap:TradingSecuritiesDebtAmortizedCost



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value36919385889394
Percentage of TradingSecuritiesDebtAmortizedCost100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentType

mktx:MutualFundsHeldInRabbiTrust



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value7555542
Percentage of TradingSecuritiesDebtAmortizedCost21.25.75.56.15.94.62.9

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value28313353567291
Percentage of TradingSecuritiesDebtAmortizedCost78.834.236.062.363.777.297.1

us-gaap:TreasuryStockShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value2222222222222222222222111111111111114
Percentage of TreasuryStockShares100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Line plots across dimensions of each concept

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ProductOrService


us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementGeographical


us-gaap:StockholdersEquity us-gaap:StatementEquityComponents


us-gaap:PropertyPlantAndEquipmentNet us-gaap:StatementGeographical


us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass


us-gaap:StockholdersEquity us-gaap:StatementEquityComponents