MRTX


Line plots across dimensions of each concept
Line plots across concepts
Tables

Table of contents



us-gaap:CommonStockValue
us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType
us-gaap:CommonStockParOrStatedValuePerShare

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfShareOutstandingBasicAndDiluted

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareBasicAndDiluted

us-gaap:AllocatedShareBasedCompensationExpense
us-gaap:IncomeStatementLocation

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:GeneralAndAdministrativeExpense

us-gaap:NetIncomeLoss
us-gaap:StatementEquityComponents

us-gaap:OperatingExpenses

us-gaap:OperatingIncomeLoss

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:ResearchAndDevelopmentExpense
mrtx:ResearchandDevelopmentArrangementDiscoveryandCollaborationAgreementTypeAxis, us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax

us-gaap:Revenues

us-gaap:Assets

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:AssetsCurrent

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:MarketableSecuritiesCurrent

us-gaap:PrepaidExpenseAndOtherAssetsCurrent

us-gaap:PropertyPlantAndEquipmentGross
us-gaap:PropertyPlantAndEquipmentByType

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:LongTermInvestments

us-gaap:OperatingLeaseRightOfUseAsset
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:OtherAssetsNoncurrent

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent

us-gaap:AccountsPayableCurrent

us-gaap:AccruedLiabilitiesCurrent

us-gaap:ContractWithCustomerLiabilityCurrent
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

us-gaap:LiabilitiesCurrent

us-gaap:OtherAccruedLiabilitiesCurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:OperatingLeaseLiability

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:CommonStockValue

us-gaap:AdditionalPaidInCapital

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:StockIssuedDuringPeriodValueNewIssues
us-gaap:StatementEquityComponents

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:StatementEquityComponents

us-gaap:ShareBasedCompensation

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquireInvestments

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:DeferredTaxAssetsNet
us-gaap:IncomeTaxAuthority
us-gaap:UnrecognizedTaxBenefits

us-gaap:DeferredTaxAssetsValuationAllowance

mrtx:AdjustmentstoAdditionalPaidinCapitalDisgorgementofStockholdersShortSwingProfits
us-gaap:StatementEquityComponents
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject
mrtx:CollaborationArrangementResearchAndDevelopmentArrangementTransactionPrice
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject
mrtx:CollaborationArrangementResearchAndDevelopmentArrangementUpFrontFeeReceived

mrtx:ConsiderationEarnedFromLicenseAgreementNoncash

mrtx:IncreaseDecreaseInOperatingLeaseLiability

mrtx:IncreaseDecreaseInRightOfUseAssets

mrtx:PaymentsForTenantImprovementsNoncash

mrtx:ProceedsfromDisgorgementofStockholdersShortSwingProfits
us-gaap:StatementEquityComponents
mrtx:StockIssuedDuringPeriodValueWarrantsExercisedNoncash

us-gaap:CapitalExpendituresIncurredButNotYetPaid
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject
us-gaap:ContractWithCustomerLiabilityRevenueRecognized

us-gaap:Depreciation
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:ResearchAndDevelopmentArrangementContractToPerformForOthersByType
us-gaap:IncreaseDecreaseInContractWithCustomerLiability

us-gaap:IncreaseDecreaseInOtherCurrentAssets

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets

us-gaap:InvestmentIncomeNetAmortizationOfDiscountAndPremium
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:OperatingLeaseExpense
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty, us-gaap:PropertyPlantAndEquipmentByType

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
us-gaap:StatementEquityComponents

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions

us-gaap:ProceedsFromSaleMaturityAndCollectionsOfInvestments

us-gaap:ProceedsFromStockOptionsExercised

us-gaap:ProceedsFromStockPlans

us-gaap:SaleOfStockConsiderationReceivedOnTransaction
us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueEmployeeStockPurchasePlan
us-gaap:StatementEquityComponents

us-gaap:UnrealizedGainLossOnInvestments

mrtx:AccruedClinicalExpense

mrtx:AccruedDevelopmentExpense

mrtx:AccruedDevelopmentandOtherExpense

mrtx:AccruedManufacturingExpense
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:ResearchAndDevelopmentArrangementContractToPerformForOthersByType
mrtx:CollaborationArrangementResearchAndDevelopmentArrangementContractToPerformForOthersCompensationExpectedToBeEarned

mrtx:CollaborativeArrangementCollaborationReceivable

mrtx:ContractwithCustomerLiabilityCurrentandOtherLiabilitiesCurrent

mrtx:DeferredTaxAssetsLeaseLiability

mrtx:DeferredTaxAssetsScientificResearchAndExperimentalDevelopmentExpenditures

mrtx:DeferredTaxAssetsTangibleAndIntangibleDepreciableAssets

mrtx:DeferredTaxLiabilitiesOperatingRightofUseAsset

mrtx:DepositsPaidForResearchAndDevelopment
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:FairValueByFairValueHierarchyLevel
mrtx:LicenseAgreementOneTimeNonCashPayment

mrtx:SaleofStockAggregateOfferingPrice

mrtx:SecurityDepositsAndOtherReceivables

us-gaap:AccountsPayableCurrentAndNoncurrent

us-gaap:AccruedLiabilitiesCurrentAndNoncurrent

us-gaap:AssetsFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:FinancialInstrument

us-gaap:CashAndCashEquivalentsFairValueDisclosure
us-gaap:CashAndCashEquivalents
us-gaap:CashAndCashEquivalents, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:ClassOfWarrantOrRightOutstanding
us-gaap:ClassOfWarrantOrRight, us-gaap:SubsidiarySaleOfStock
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:ResearchAndDevelopmentArrangementContractToPerformForOthersByType
us-gaap:ContractWithCustomerAssetGross
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject
us-gaap:ContractWithCustomerLiability

us-gaap:DeferredTaxAssetsCapitalLossCarryforwards

us-gaap:DeferredTaxAssetsGross

us-gaap:DeferredTaxAssetsOperatingLossCarryforwards

us-gaap:DeferredTaxAssetsTaxCreditCarryforwardsResearch

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves

us-gaap:DeferredTaxLiabilitiesInvestments

us-gaap:EmployeeRelatedLiabilitiesCurrent

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
us-gaap:AwardType
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue

us-gaap:InterestReceivableCurrent

us-gaap:InvestmentsFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FinancialInstrument
us-gaap:FinancialInstrument
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear
us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty
us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent
mrtx:ExpirationPeriod, us-gaap:IncomeTaxAuthority
us-gaap:OperatingLossCarryforwards
us-gaap:IncomeTaxAuthority

us-gaap:PrepaidExpenseCurrent

us-gaap:RestrictedCash

us-gaap:RestrictedCashNoncurrent
us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:SubsequentEventType
us-gaap:SaleOfStockPricePerShare

us-gaap:SecurityDeposit
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
us-gaap:PlanName
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
us-gaap:AwardType
us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
us-gaap:IncomeTaxAuthority, us-gaap:TaxCreditCarryforward
us-gaap:TaxCreditCarryforwardAmount

Plots across concepts


IncomeStatement
Net Income Loss
Balance Sheet
Operating Lease Right Of Use Asset
Assets
Property Plant And Equipment Net
Current Assets
Prepaid Expense And Other Assets Current
NonCurrent Assets
Long Term Investments
PropertyPlantAndEquipmentNet
Accumulated Depreciation Depletion And Amortization Property Plant And Equipment
Liabilities
Liabilities Current
Current Liabilities
Other Accrued Liabilities Current
Stockholders Equity
Retained Earnings Accumulated Deficit
CashFlow
Net Income Loss
NetCashProvidedByUsedInOperatingActivities
Net Income Loss
NetCashProvidedByUsedInInvestingActivities
Payments To Acquire Property Plant And Equipment
Shares
Weighted Average Number Of Share Outstanding Basic And Diluted

Tables

  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:CommonStockValue █▇▇▆▅▅▅▄▃▃▃▂▂▁▁▁0.050.0450.0450.0440.040.0390.0390.0360.0330.0330.0320.0290.0290.0250.0250.025
 us-gaap:CommonStockParOrStatedValuePerShare us-gaap:StatementClassOfStock,us-gaap:SubsequentEventType us-gaap:CommonClassA,us-gaap:SubsequentEventNANANANANANANANANANANANANANANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding NANA43.825723NANANANANANANANANANANANANA
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic NANA43.825723NANANANANANANANANANANANANA
us-gaap:WeightedAverageNumberOfShareOutstandingBasicAndDiluted NA44.61422643.82572342.886691NA39.19721336.17360534.980361NA32.41040729.75798628.843578NA24.97090524.95001224.383941
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount NA11.50878611.73660311.867124NA12.31387812.78966113.322595NA14.03278613.25467512.854625NA7.2695997.2563686.450612
 us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities us-gaap:EmployeeStockOptionNA2.4159792.112692.174353NA2.4871352.3719082.316993NA2.2150861.7660471.458774NA0.0125910.00.0
 us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities us-gaap:RestrictedStockUnitsRSUNANA0.311269NANANANANANANANANANANANANA
 us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities us-gaap:WarrantNA9.0928079.6239139.692771NA9.82674310.41775311.005602NA11.817711.48862811.395851NA7.2570087.2563686.450612
us-gaap:EarningsPerShareBasic NANA-1.89NANANANANANANANANA-0.67-0.65-0.74-0.73
us-gaap:EarningsPerShareDiluted NANA-1.89NANANANANANANANANANANANANA
us-gaap:EarningsPerShareBasicAndDiluted ▁▂▂▁▂▄▅▅▆▆▆█▇▇▇▇-2.08-1.96-1.89-2.02-1.83-1.38-1.26-1.17-0.87-0.85-0.94-0.51-0.67-0.65-0.74-0.73
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:AllocatedShareBasedCompensationExpense ████▆▆▅▄▂▂▂▂▁▁▁▁21.74321.75120.78721.56716.71115.10612.58911.1314.2624.0583.8743.661.3181.4792.2231.766
us-gaap:ComprehensiveIncomeNetOfTax ▁▂▃▂▃▅▆▆▇▇▇█████-101.785-88.163-81.282-86.837-72.378-54.17-45.544-40.754-28.237-27.469-27.715-14.997-17.93-16.337-18.443-17.775
us-gaap:GeneralAndAdministrativeExpense █▆▆▆▄▃▃▃▂▂▂▂▁▁▁▁25.33820.24919.77918.04612.23310.6859.8949.7626.3735.3134.8415.1542.9833.1193.6543.693
us-gaap:NetIncomeLoss ▁▂▂▂▃▅▅▆▇▇▇█████-101.087-87.336-82.859-86.655-72.376-54.273-45.695-40.912-28.272-27.568-27.869-14.709-17.895-16.35-18.339-17.846
 us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings▁▃▃▃▄▆▇█-101.087-87.336-82.859-86.655-72.376-54.273-45.695-40.912NA-27.568-27.869-14.709NANANANA
us-gaap:OperatingExpenses █▇▆▇▅▄▃▃▂▂▂▂▁▁▁▁108.043100.10284.86289.75475.17458.04748.21844.00233.13128.93928.6724.81318.22716.60118.61618.09
us-gaap:OperatingIncomeLoss ▁▂▃▂▃▅▆▆▇▇▇█████-106.336-88.678-84.862-89.487-74.646-57.059-47.641-42.758-29.672-28.939-28.67-15.346-18.228-16.601-18.616-18.09
us-gaap:OtherNonoperatingIncomeExpense █▃▃▅▄▅▃▃▃▃▂▂▁▁▁▁5.2481.3422.0032.8322.2722.7861.9461.8461.41.3710.8010.6370.3320.2510.2770.244
us-gaap:ResearchAndDevelopmentExpense ██▆▇▆▄▄▃▂▂▂▂▁▁▁▁82.70579.85365.08371.70862.94147.36238.32434.2426.75823.62623.82919.65915.24413.48214.96214.397
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax ▂█▁▁▁▂▁▂▃▁▁▇▁▁▁▁1.70711.4240.00.2670.5260.9880.5771.2443.4590.00.09.4670.00.00.00.0
us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax NA11.4240.00.267NA0.9880.5771.244NA0.00.0NANA0.0NANA
us-gaap:Revenues ▂█▁▁▁▂▁▂▃▁▁▇▁▁▁▁1.70711.4240.00.2670.5260.9880.5771.2443.4590.00.09.4670.00.00.00.0
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:Assets █▄▄▄▃▃▃▂▂▂▂▁▁▁▁▁1476.128619.851663.95713.447432.2470.698501.456309.361228.454247.693265.187154.544157.24682.06194.984110.765
us-gaap:Liabilities █▅▄▄▄▃▂▂▂▂▁▁▁▁▁▁115.33968.90858.94657.22149.90536.20928.97525.80726.87822.60418.84316.70313.95813.90912.01711.649
us-gaap:LiabilitiesAndStockholdersEquity █▄▄▄▃▃▃▂▂▂▂▁▁▁▁▁1476.128619.851663.95713.447432.2470.698501.456309.361228.454247.693265.187154.544157.24682.06194.984110.765
us-gaap:StockholdersEquity █▄▄▄▃▃▃▂▂▂▂▁▁▁▁▁1360.789550.943605.004656.226382.295434.489472.481283.554201.576225.089246.344137.841143.28868.15282.96799.116
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:AssetsCurrent █▄▄▄▃▃▃▂▂▂▂▁▁▁▁▁1403.643595.391654.037704.816424.407464.648495.71306.382226.66246.098263.596153.073155.75979.40192.277107.925
us-gaap:CashAndCashEquivalentsAtCarryingValue █▂▂▂▁▂▃▁▁▂▂▁▂▁▁▁885.562131.434131.689204.50546.53591.904252.09274.60532.694116.71105.96320.567107.70320.78419.95529.757
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents █▂▂▂▁▁▃▁▁▂▂886.182132.054132.309204.82646.85692.224252.09274.60532.694116.71105.963NA107.703NANANA
us-gaap:MarketableSecuritiesCurrent █▇██▆▆▄▄▃▂▃▂▁▁▁▁504.544447.616514.021490.855368.515362.308233.435226.38190.096125.902154.221128.08543.13454.17867.88375.703
us-gaap:PrepaidExpenseAndOtherAssetsCurrent ▇█▄▅▄▅▅▂▂▂▁▂▂▂▂▁13.53716.3418.3279.4569.35710.43610.1835.3973.873.4863.4124.4214.9224.4394.4392.465
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:PropertyPlantAndEquipmentGross █▆▄▃▂▁▁▁▁▁▁▁▁▁▁▁9.4797.3654.4693.4372.8051.4731.3221.2531.2531.1671.3361.3361.3361.3361.3361.31
us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment █▇▅▄▄▃▂▂▂▁▃▂▂▂▁▁1.671.4641.2821.1541.0290.9370.8790.8240.780.7380.8910.8520.8110.7650.7180.672
us-gaap:PropertyPlantAndEquipmentNet █▆▄▃▂▁▁▁▁▁▁▁▁▁▁▁7.8095.9013.1872.2831.7760.5360.4430.4290.4730.4290.4450.4840.5250.5710.6180.638
us-gaap:LongTermInvestments █▁15.62911.4NANANANANANANANANANANANANANA
us-gaap:OperatingLeaseRightOfUseAsset █▁▁▁▁▁▁▁▁39.890.60.70.40.60.3410.2040.2870.0NANANANANANANA
us-gaap:OtherAssetsNoncurrent █▆▆▆▅▅▅▂▁▁▁▁▁▂▂▂9.1577.1596.7266.3486.0175.5145.3032.551.3211.1661.1460.9870.9622.0892.0892.202
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent █▇▆▆▅▄▃▃▃▂▂▂▁▁▁▁71.47266.6756.84355.4548.08234.68927.68524.46525.77521.50217.81115.76113.64413.5811.73711.282
us-gaap:AccountsPayableCurrent ▆▅█▃▅▄▄▃▃▂▂▂▂▁▁▁18.11715.97524.0999.58716.36712.56810.50710.0678.5316.8434.2664.7314.3442.7293.9733.45
us-gaap:AccruedLiabilitiesCurrent 53.355NANANA21.29NANANA10.15411.29411.0259.0586.2566.085.6025.788
us-gaap:ContractWithCustomerLiabilityCurrent NANANANA0.824NANA0.6380.3710.4390.3180.2290.0NANANA
 us-gaap:ContractWithCustomerLiabilityCurrent us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject mrtx:ZaiCollaborationAndLicenseAgreementNANANANANANANANANANANANANANANANA
us-gaap:LiabilitiesCurrent ██▆▆▅▄▃▃▃▂▂▂▁▁▁▁71.47267.36757.69556.04748.90635.33628.21425.10326.14621.94118.12916.0113.64413.5811.73711.282
us-gaap:OtherAccruedLiabilitiesCurrent 1.712NANANANANANANANANANANA0.0232.1270.0190.016
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:OtherLiabilitiesNoncurrent █▅▃▂▁1.9621.5411.2511.1740.999NANANA0.6NANA0.40.314NANANA
us-gaap:OperatingLeaseLiabilityNoncurrent 41.905NANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty mrtx:CurrentHeadquarters1.681NANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty mrtx:CurrentHeadquarters7.844NANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty mrtx:CurrentHeadquarters8.08NANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty mrtx:CurrentHeadquarters8.322NANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty mrtx:CurrentHeadquarters68.257NANANANANANANANANANANANANANANA
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:StockholdersEquity █▄▄▄▃▃▃▂▂▂▂▁▁▁▁▁1360.789550.943605.004656.226382.295434.489472.481283.554201.576225.089246.344137.841143.28868.15282.96799.116
us-gaap:CommonStockValue █▇▇▆▅▅▅▄▃▃▃▂▂▁▁▁0.050.0450.0450.0440.040.0390.0390.0360.0330.0330.0320.0290.0290.0250.0250.025
us-gaap:AdditionalPaidInCapital █▅▅▅▃▃▃▂▂▂▂▁▁▁▁▁2481.2181569.5921535.491505.4311144.6671124.4841108.306873.838751.109746.385740.172603.957594.407501.346499.824497.531
us-gaap:RetainedEarningsAccumulatedDeficit ▁▂▃▄▄▅▆▆▇▇▇▇▇███-1130.238-1029.151-941.815-858.956-772.301-699.925-645.652-599.957-559.045-530.773-503.205-475.336-460.627-442.733-426.383-408.044
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▃▅█▃▃▃▃▂▂▂▂▁▂▂▂▂9.75910.45711.2849.7079.8899.8919.7889.6379.4799.4449.3459.1919.4799.5149.5019.604
us-gaap:StockIssuedDuringPeriodValueNewIssues █▁▁▄▁▁▃▂879.5990.00.0323.9770.020.0219.927107.883NANA130.66NANANANANA
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue ██▇█▅▄▂▁21.74321.75120.78721.56716.71115.10612.58911.131NA4.0583.8743.66NANANANA
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▁▁▃▃▅▅▅▅▇▇▇█▇▇▇▇-76.421-76.763-59.343-59.004-41.902-32.874-38.468-34.482-20.795-20.172-21.181-7.948-13.766-15.091-17.617-18.232
us-gaap:NetCashProvidedByUsedInInvestingActivities ▄█▅▁▅▁▅▄▃▇▅▃▆▆▆▄-59.3464.157-22.447-122.227-6.939-128.066-5.927-35.208-63.68328.762-25.766-85.07811.04413.7717.744-41.21
us-gaap:NetCashProvidedByUsedInFinancingActivities █▁▁▄▁▁▃▂▁▁▂▁▂▁▁▂889.88912.3519.273339.2013.4731.072221.882111.6010.4622.157132.3435.8989.6412.1490.07166.816
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect █▂▂▃▂▁▄▃▂▂754.128-0.255-72.517157.97-45.368-159.868177.48741.911-84.01610.747NANANANANANA
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▁▁▃▃▅▅▅▅▇▇▇█▇▇▇▇-76.421-76.763-59.343-59.004-41.902-32.874-38.468-34.482-20.795-20.172-21.181-7.948-13.766-15.091-17.617-18.232
us-gaap:NetIncomeLoss ▁▂▂▂▃▅▅▆▇▇▇█████-101.087-87.336-82.859-86.655-72.376-54.273-45.695-40.912-28.272-27.568-27.869-14.709-17.895-16.35-18.339-17.846
 us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings▁▃▃▃▄▆▇█-101.087-87.336-82.859-86.655-72.376-54.273-45.695-40.912NA-27.568-27.869-14.709NANANANA
us-gaap:ShareBasedCompensation ████▆▆▅▄▂▂▂▂▁▁▁▁21.74321.7520.78721.56716.71115.10612.58911.1314.2624.0583.8743.661.3181.4792.2231.766
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ▄█▅▁▅▁▅▄▃▇▅▃▆▆▆▄-59.3464.157-22.447-122.227-6.939-128.066-5.927-35.208-63.68328.762-25.766-85.07811.04413.7717.744-41.21
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ██▇▂▇▂▁▁▁▁1.5061.4361.2010.2241.3320.1510.0690.00.0860.036NANA0.0010.00.080.0
us-gaap:PaymentsToAcquireInvestments ▇▃▅█▃█▃▅▄▁▂▄▁▁▂▃206.21672.481153.743230.38472.113245.44985.208127.458100.024.43948.516102.825.4558.67923.11463.31
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities █▁▁▄▁▁▃▂▁▁▂▁▂▁▁▂889.88912.3519.273339.2013.4731.072221.882111.6010.4622.157132.3435.8989.6412.1490.07166.816
  2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value52000.051000.050000.045000.045000.044000.040000.039000.039000.036000.033000.033000.032000.029000.029000.025000.025000.025000.020000.020000.020000.020000.019000.019000.016000.016000.014000.014000.014000.013000.013000.010000.010000.010000.0
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.00.0

Common Stock Par Or Stated Value Per Share

us-gaap:CommonStockParOrStatedValuePerShare us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType

us-gaap:CommonStockParOrStatedValuePerShare

us-gaap:CommonClassA, us-gaap:SubsequentEvent


Common
Period End2020-07-02
Value0.001
Percentage of CommonStockParOrStatedValuePerShare100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding


Weighted
Period End2021-06-302020-06-302015-09-302014-09-302014-03-312013-09-302013-03-31
Value51431614139.95789610
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic


Weighted
Period End2021-06-302020-06-302015-09-302014-09-302014-03-312013-09-302013-03-31
Value51431613139.9578969.957739
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Share Outstanding Basic And Diluted

us-gaap:WeightedAverageNumberOfShareOutstandingBasicAndDiluted

us-gaap:WeightedAverageNumberOfShareOutstandingBasicAndDiluted


Weighted
Period End2021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-06-302014-03-312013-09-302013-06-302012-09-302012-06-30
Value5044434239363432292824242419191916161513139.9578969.9577256.3610936.358266
Percentage of WeightedAverageNumberOfShareOutstandingBasicAndDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount


Antidilutive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value10101111111212131413127.2695997.2563686.4506120.00.6079921.3267882.0943382.3467582.0831750.5333981.8313391.8748420.5331580.00.00.800588
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities

us-gaap:EmployeeStockOption


Antidilutive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value2.3320082.7584152.4159792.112692.1743532.4871352.3719082.3169932.2150861.7660471.4587740.0125910.00.00.00.2555510.4384570.6343210.5546890.3812860.2526780.2725380.2227620.0513930.00.00.028904
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount22.125.521.018.018.320.218.517.415.813.311.30.20.00.00.042.033.030.323.618.347.414.911.99.60.00.03.6

us-gaap:RestrictedStockUnitsRSU


Antidilutive
Period End2021-06-302020-06-30
Value0.6058780.311269
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount5.72.7

us-gaap:Warrant


Antidilutive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-30
Value7.6057648.0430049.0928079.6239139.6927719.82674310111111117.2570087.2563686.4506120.00.3524410.8883311.4600171.7920691.7018890.280721.5588011.652080.4817650.00.00.771684
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount72.174.579.082.081.779.881.582.684.286.788.799.8100.0100.00.058.067.069.776.481.752.685.188.190.40.00.096.4

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic


Earnings
Period End2021-06-302020-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value-3.23-1.89-0.67-0.65-0.74-0.73-0.99-0.97-1.11-1.13-0.96-1.11000-0.640-1.010-2.950-0.42
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.00.0100.00.0100.00.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted


Earnings
Period End2021-06-302020-06-302015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value-3.23-1.89-0.96-1.11000-0.720-1.01-960.0-2.95-800.0-0.68
Percentage of EarningsPerShareDiluted100.0100.0100.0100.00.00.00.0100.00.0100.0100.0100.0100.0100.0

Earnings Per Share Basic And Diluted

us-gaap:EarningsPerShareBasicAndDiluted

us-gaap:EarningsPerShareBasicAndDiluted


Earnings
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-06-302014-03-312013-12-312013-09-302013-06-302012-12-312012-09-302012-06-30
Value-2.67-2.08-1.96-1.89-2.02-1.83-1.38-1.26-1.17-0.87-0.85-0.94-0.51-0.67-0.65-0.74-0.73-0.99-0.97-1.11-1.13-1.11-0.95-0.77-0.82-1.01-0.6-2.95-0.81-0.8-0.93-0.73
Percentage of EarningsPerShareBasicAndDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Allocated Share Based Compensation Expense

us-gaap:AllocatedShareBasedCompensationExpense

us-gaap:AllocatedShareBasedCompensationExpense


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value272421212021161512114.2624.0583.8743.661.3181.4792.2231.7662.5382.762.2883.0382.3422.8042.7922.3162.2282.5911.2850.9461.1961.751-0.2170.462
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.01273.8190.40.08077.53177.01528.92181.8894.8123.20.00.038.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AllocatedShareBasedCompensationExpense us-gaap:IncomeStatementLocation

us-gaap:GeneralAndAdministrativeExpense


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value11109.569.1959.339.7196.1036.4585.9785.9742.1432.2092.1032.1670.630.8951.2850.7841.3741.3990.811.581.3711.8451.8611.5081.5921.7320.7030.4580.9121.857-0.1430.321
Percentage of AllocatedShareBasedCompensationExpense41.141.244.042.344.945.136.542.847.553.750.354.454.359.247.860.557.844.454.150.735.452.058.565.866.765.171.566.854.748.476.3106.165.969.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0560.080.50.03640.11160.3653.61036.0480.262.00.00.022.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:GeneralAndAdministrativeExpense0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ResearchAndDevelopmentExpense


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value161412121111108.6486.6115.1572.1191.8491.7711.4930.6880.5840.9380.9821.1641.3611.4781.4580.9710.9590.9310.8080.6360.8590.5820.4880.284-0.106-0.0740.141
Percentage of AllocatedShareBasedCompensationExpense58.958.856.057.755.154.963.557.252.546.349.745.645.740.852.239.542.255.645.949.364.648.041.534.233.334.928.533.245.351.623.7-6.134.130.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0713.7109.90.04437.52016.7875.31145.8414.561.30.00.015.80.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ResearchAndDevelopmentExpense0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value-166280000.0-135980000.0-101780000.0-88163000.0-81282000.0-86837000.0-72378000.0-54170000.0-45544000.0-40754000.0-28237000.0-27469000.0-27715000.0-14997000.0-17930000.0-16337000.0-18443000.0-17775000.0-19773000.0-19455000.0-22028000.0-21887000.0-18382000.0-18735000.0-15455000.0-11935000.0-10395000.0-8629000.0-11014000.0-13646000.0-11246000.0-29398000.0-8012000.0-4217000.0
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-5962.8-771.70.0-32523.2-13760.1-5482.8-7893.2-3276.0-816.30.00.0-158.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

General And Administrative Expense

us-gaap:GeneralAndAdministrativeExpense

us-gaap:GeneralAndAdministrativeExpense


General
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value29282520191812109.8949.7626.3735.3134.8415.1542.9833.1193.6543.6933.9013.4753.7864.133.5754.1614.243.7793.8443.5192.8782.4152.5283.712.3822.5241.3751.7171.082
Percentage of GeneralAndAdministrativeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.01484.4177.20.06758.82325.71081.51714.7784.7184.20.00.054.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-166430000.0-135680000.0-101090000.0-87336000.0-82859000.0-86655000.0-72376000.0-54273000.0-45695000.0-40912000.0-28272000.0-27568000.0-27869000.0-14709000.0-17895000.0-16350000.0-18339000.0-17846000.0-19722000.0-19421000.0-22061000.0-21914000.0-18417000.0-18741000.0-15446000.0-11940000.0-10387000.0-8617000.0-11038000.0-13656000.0-11233000.0-29398000.0-8012000.0-4217000.0-6307000.0-5946000.0-4677000.0
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-5921.9-764.50.0-32455.1-13759.7-5493.2-7919.4-3288.7-817.30.00.0-155.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-166430000.0-135680000.0-101090000.0-87336000.0-82859000.0-86655000.0-72376000.0-54273000.0-45695000.0-40912000.0-27568000.0-27869000.0-14709000.0
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-5921.9-764.50.0-32455.1-13759.7-5493.2-7919.4-3288.70.00.0-155.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.0

Operating Expenses

us-gaap:OperatingExpenses

us-gaap:OperatingExpenses


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value164132108100848975584844332828241816181819192222181815111010107.9567.8739.2026.8927.9996.3515.9664.734
Percentage of OperatingExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.06329.4876.20.033615.714291.65875.28356.73537.1957.80.00.0262.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Operating Income Loss

us-gaap:OperatingIncomeLoss

us-gaap:OperatingIncomeLoss


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-164190000.0-132420000.0-106340000.0-88678000.0-84862000.0-89487000.0-74646000.0-57059000.0-47641000.0-42758000.0-29672000.0-28939000.0-28670000.0-15346000.0-18228000.0-16601000.0-18616000.0-18090000.0-19853000.0-19581000.0-22227000.0-22118000.0-18488000.0-18724000.0-15516000.0-11986000.0-10443000.0-10548000.0-10114000.0-7956000.0-7886000.0-9202000.0-6892000.0-7999000.0-6351000.0-5966000.0-4734000.0
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-6229.4-776.20.0-33515.7-14191.3-5775.2-8256.7-3437.1-857.80.00.0-162.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:OtherNonoperatingIncomeExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-2.244-3.2595.2481.3422.0032.8322.2722.7861.9461.8461.41.3710.8010.6370.3320.2510.2770.2440.1310.160.1660.2040.071-0.0170.070.0460.0290.0240.052-0.22516-20.141-1.079-0.570.0560.0340.07
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0307.411.70.01060.7431.9282.0337.3148.440.50.00.06.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Research And Development Expense

us-gaap:ResearchAndDevelopmentExpense

us-gaap:ResearchAndDevelopmentExpense


Research
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value13410482796571624738342623231915131414151618171414118.2076.5997.0297.2365.2074.325.4924.515.4754.9764.2493.652
Percentage of ResearchAndDevelopmentExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.04845.0699.00.026856.911966.04793.76641.92752.4773.60.00.0207.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ResearchAndDevelopmentExpense mrtx:ResearchandDevelopmentArrangementDiscoveryandCollaborationAgreementTypeAxis, us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

mrtx:MilestonePaymentsInitiationOfFirstPhase2TrialForMRTX849, mrtx:PfizerDiscoveryandCollaborationAgreement


Research
Period End2020-12-31
Value0.0
Percentage of ResearchAndDevelopmentExpense0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mrtx:MilestonePaymentsInitiationOfFirstPhase2TrialForMRTX849 mrtx:PfizerDiscoveryandCollaborationAgreement0.0

mrtx:MilestonePaymentsInitiationOfFirstRegulatoryToxicologyStudyForMRTX1133, mrtx:PfizerDiscoveryandCollaborationAgreement


Research
Period End2020-12-31
Value0.0
Percentage of ResearchAndDevelopmentExpense0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mrtx:MilestonePaymentsInitiationOfFirstRegulatoryToxicologyStudyForMRTX1133 mrtx:PfizerDiscoveryandCollaborationAgreement0.0

mrtx:ResearchandDevelopmentServices, mrtx:PfizerDiscoveryandCollaborationAgreement


Research
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.00.00.01.51.51.51.51.5
Percentage of ResearchAndDevelopmentExpense0.00.00.02.12.43.23.94.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.0561.8285.2151.8260.0120.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mrtx:ResearchandDevelopmentServices mrtx:PfizerDiscoveryandCollaborationAgreement0.00.00.00.00.00.00.00.0

us-gaap:ResearchAndDevelopmentExpense us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

mrtx:PfizerDiscoveryandCollaborationAgreement


Research
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value5.00.00.30.04.51.51.51.52.5
Percentage of ResearchAndDevelopmentExpense3.70.00.40.06.32.43.23.97.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.02.60.01685.4285.2151.8260.0201.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax mrtx:PfizerDiscoveryandCollaborationAgreement0.00.00.00.00.00.00.00.00.0

Revenue From Contract With Customer Excluding Assessed Tax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax


Revenue
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1.707110.00.2670.5260.9880.5771.2443.4590.00.09.4670.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.00.0100.0100.0100.0100.0100.0100.00.00.0100.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.00.0100.0100.0100.0100.0100.0100.00.00.0100.00.00.00.00.0

Revenue From Contract With Customer Including Assessed Tax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax


Revenue
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302017-09-30
Value110.00.2670.9880.5771.2440.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.00.0100.0100.0100.0100.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.00.0100.0100.0100.0100.00.00.00.0

Revenues

us-gaap:Revenues

us-gaap:Revenues


Revenues
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1.707110.00.2670.5260.9880.5771.2443.4590.00.09.4670.00.00.00.0
Percentage of Revenues100.0100.00.0100.0100.0100.0100.0100.0100.00.00.0100.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.00.0100.0100.0100.0100.0100.0100.00.00.0100.00.00.00.00.0

Assets

us-gaap:Assets

us-gaap:Assets


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value135513801476619663713432470501309228247265154157829411063799511212814361723341495664182339
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities

us-gaap:Liabilities


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value226121115685857493628252622181613131211151313109.8419.8217.1545.1315.4175.57144423841165.385
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets16.78.87.811.18.98.011.57.75.88.311.89.17.110.88.916.912.710.523.917.314.49.67.76.811.67.116.213.590.375.959.9230.972.913.5

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:LiabilitiesAndStockholdersEquity


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value135513801476619663713432470501309228247265154157829411063799511212814361723341495664182339
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-312011-12-31
Value112812591360550605656382434472283201225246137143688299486582101118133546728354.8251325-23.5616.2373427
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets83.391.292.288.991.192.088.592.394.291.788.290.992.989.291.183.187.389.576.182.785.690.492.393.288.492.983.886.59.724.140.1-130.927.186.50.0

us-gaap:StockholdersEquity us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value9.6019.4569.75910119.7079.8899.8919.7889.6379.4799.4449.3459.1919.4799.5339.5589.5219.5079.528.945
Percentage of StockholdersEquity0.90.80.71.91.91.52.62.32.13.44.74.23.86.76.619.78.133.936.727.732.8
Percentage of Assets0.70.70.71.71.71.42.32.12.03.14.13.83.55.96.015.07.528.414.723.90.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value255125152481156915351505114411241108873751746740603594428415260214154132
Percentage of StockholdersEquity226.0199.8182.3284.9253.8229.4299.4258.8234.6308.2372.6331.6300.5438.2414.8887.0351.4928.7829.7448.1484.6
Percentage of Assets188.2182.2168.1253.2231.3211.0264.8238.9221.0282.5328.8301.3279.1390.8378.0675.4324.4778.4332.8387.50.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value0.0520.0510.050.0450.0450.0440.040.0390.0390.0360.0330.0330.0320.0290.0290.020.0190.0140.0130.010.006
Percentage of StockholdersEquity0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value-1432.348-1265.918-1130.238-1029.151-941.815-858.956-772.301-699.925-645.652-599.957-559.045-530.773-503.205-475.336-460.627-389.751-306.633-242.089-198.391-140.491-120.205
Percentage of StockholdersEquity-126.9-100.5-83.1-186.8-155.7-130.9-202.0-161.1-136.7-211.6-277.3-235.8-204.3-344.8-321.5-806.8-259.5-862.7-766.4-408.2-440.2
Percentage of Assets-105.7-91.7-76.6-166.0-141.9-120.4-178.7-148.7-128.8-193.9-244.7-214.3-189.8-307.6-292.9-614.3-239.5-723.1-307.4-353.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Assets Current

us-gaap:AssetsCurrent

us-gaap:AssetsCurrent


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value127813031403595654704424464495306226246263153155799210759759310912514160713240495664172239
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets94.394.495.196.198.598.898.298.798.999.099.299.499.499.099.196.897.297.493.995.496.997.798.098.298.498.697.597.799.099.599.594.697.498.8

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:CashAndCashEquivalentsAtCarryingValue


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value2803298851311312044691252743211610520107201929221924344910913146.5934.9158.5158.317147.6169.7410185.6438.0519.882
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets20.723.960.021.219.828.710.819.550.324.114.347.140.013.368.525.321.026.935.325.025.630.738.776.521.619.819.711.917.114.822.142.342.30.046.20.00.00.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312016-12-31
Value2813308861321322044692252743211610510722
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets20.823.960.021.319.928.710.819.650.324.114.347.140.068.535.3

Marketable Securities Current

us-gaap:MarketableSecuritiesCurrent

us-gaap:MarketableSecuritiesCurrent


Marketable
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value9159575044475144903683622332261901251541284354677534536673722845532232384547
Percentage of MarketableSecuritiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets67.669.434.272.277.468.885.377.046.673.283.250.858.282.927.466.071.568.354.167.269.665.056.919.673.574.467.879.478.380.074.1

Prepaid Expense And Other Assets Current

us-gaap:PrepaidExpenseAndOtherAssetsCurrent

us-gaap:PrepaidExpenseAndOtherAssetsCurrent


Prepaid
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value811613168.3279.4569.35710105.3973.873.4863.4124.4214.9224.4394.4392.4652.8212.5041.7262.2323.0753.0252.0163.1663.3542.6381.7442.6622.1451.511.7871.537
Percentage of PrepaidExpenseAndOtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.01.20.92.61.31.32.22.22.01.71.71.41.32.93.15.44.72.24.43.21.82.02.42.13.34.410.06.43.54.73.38.47.83.9

Property Plant And Equipment Gross

us-gaap:PropertyPlantAndEquipmentGross

us-gaap:PropertyPlantAndEquipmentGross


Property
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value9479000.07365000.04469000.03437000.02805000.01473000.01322000.01253000.01253000.01167000.01336000.01336000.01336000.01336000.01336000.01310000.01256000.01123000.01106000.01106000.01061000.01027000.01028000.0946000.0731000.0715000.0631000.0390000.03503000.03360000.0
Percentage of PropertyPlantAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.61.20.70.50.60.30.30.40.50.50.50.90.81.61.41.22.01.41.21.00.80.71.71.32.21.71.30.75.48.4

us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType

mrtx:LaboratoryEquipment


Property
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value5310000.04886000.02791000.02436000.02212000.0880000.0729000.0729000.0729000.0643000.0643000.0643000.0643000.0643000.0643000.0617000.0563000.0442000.0425000.0425000.0425000.0425000.0427000.0344000.0346000.0283000.0249000.001794000.01794000.0
Percentage of PropertyPlantAndEquipmentGross56.066.362.570.978.959.755.158.258.255.148.148.148.148.148.147.144.839.438.438.440.141.441.536.447.339.639.50.051.253.4
Percentage of Assets0.40.80.40.30.50.20.10.20.30.30.20.40.40.80.70.60.90.60.40.40.30.30.70.51.00.70.50.02.84.5
Percentage of Assets mrtx:LaboratoryEquipment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ComputerEquipment


Property
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value201000.0201000.0201000.0201000.0201000.0201000.0201000.0201000.0201000.0200000.0329000.0329000.0329000.0329000.0329000.0329000.0329000.0329000.0329000.0329000.0329000.0329000.0328000.0329000.0329000.0325000.0305000.0305000.01534000.01421000.0
Percentage of PropertyPlantAndEquipmentGross2.12.74.55.87.213.615.216.016.017.124.624.624.624.624.625.126.229.329.729.731.032.031.934.845.045.548.378.243.842.3
Percentage of Assets0.00.00.00.00.00.00.00.10.10.10.10.20.20.40.30.30.50.40.30.30.30.20.50.51.00.80.60.52.43.6
Percentage of Assets us-gaap:ComputerEquipment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConstructionInProgress


Property
Period End2020-09-30
Value1886000.0
Percentage of PropertyPlantAndEquipmentGross25.6
Percentage of Assets0.3
Percentage of Assets us-gaap:ConstructionInProgress0.0

us-gaap:LeaseholdImprovements


Property
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value3639000.063000.063000.063000.063000.063000.063000.063000.063000.063000.063000.063000.063000.063000.063000.063000.063000.051000.051000.051000.051000.051000.051000.051000.0051000.021000.042000.053000.056000.0
Percentage of PropertyPlantAndEquipmentGross38.40.91.41.82.24.34.85.05.05.44.74.74.74.74.74.85.04.54.64.64.85.05.05.40.07.13.310.81.51.7
Percentage of Assets0.20.00.00.00.00.00.00.00.00.00.00.00.00.10.10.10.10.10.10.00.00.00.10.10.00.10.00.10.10.1
Percentage of Assets us-gaap:LeaseholdImprovements0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OfficeEquipment


Property
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value329000.0329000.0329000.0329000.0329000.0329000.0329000.0260000.0260000.0261000.0301000.0301000.0301000.0301000.0301000.0301000.0301000.0301000.0301000.0301000.0256000.0222000.0222000.0222000.056000.056000.056000.043000.0122000.089000.0
Percentage of PropertyPlantAndEquipmentGross3.54.57.49.611.722.324.920.820.822.422.522.522.522.522.523.024.026.827.227.224.121.621.623.57.77.88.911.03.52.6
Percentage of Assets0.00.10.00.00.10.10.10.10.10.10.10.20.20.40.30.30.50.40.30.30.20.20.40.30.20.10.10.10.20.2
Percentage of Assets us-gaap:OfficeEquipment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment


Accumulated
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value1670000.01464000.01282000.01154000.01029000.0937000.0879000.0824000.0780000.0738000.0891000.0852000.0811000.0765000.0718000.0672000.0627000.0586000.0548000.0505000.0447000.0388000.0335000.0279000.0235000.0191000.0152000.0115000.03181000.03027000.0
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.10.20.20.20.20.20.20.30.30.30.30.60.50.90.80.61.00.70.60.40.30.30.50.40.70.50.30.24.97.6

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:PropertyPlantAndEquipmentNet


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value129.0617.8095.9013.1872.2831.7760.5360.4430.4290.4730.4290.4450.4840.5250.5710.6180.6380.6290.5370.5580.6010.6140.6390.6930.6670.4960.5240.4790.2750.3220.4270.4250.333
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.90.70.51.00.50.30.40.10.10.10.20.20.20.30.30.70.70.61.00.70.60.50.50.41.10.91.51.31.00.50.52.41.80.8

Long Term Investments

us-gaap:LongTermInvestments

us-gaap:LongTermInvestments


Long
Period End2021-06-302021-03-312020-12-312020-09-30
Value8.947111511
Percentage of LongTermInvestments100.0100.0100.0100.0
Percentage of Assets0.70.81.11.8

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OperatingLeaseRightOfUseAsset


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value3839390.60.70.40.60.3410.2040.2870.0
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets2.92.82.70.10.10.10.10.10.00.10.0

us-gaap:OperatingLeaseRightOfUseAsset us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

mrtx:CurrentHeadquarters


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value3839390.60.70.40.60.3
Percentage of OperatingLeaseRightOfUseAsset100.0100.1100.0100.0100.0100.0100.088.0
Percentage of Assets2.92.82.70.10.10.10.10.1
Percentage of Assets mrtx:CurrentHeadquarters0.00.00.00.00.00.00.00.0

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent

us-gaap:OtherAssetsNoncurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-312012-12-31
Value17179.1577.1596.7266.3486.0175.5145.3032.551.3211.1661.1460.9870.9622.0892.0892.2023.263.1352.3962.0012.0012.0010.2880.3260.3260.440.0240.00.139
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0
Percentage of Assets1.31.30.61.21.00.91.41.21.10.80.60.50.40.60.62.52.22.05.14.02.51.81.61.40.50.51.01.10.00.00.3

Accounts Payable And Accrued Liabilities Current

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent


Accounts
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value71665655483427242521171513131111151313109.7989.7697.0965.1115.3965.4045.9153.9835.2456.5554.5165.272
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.810.88.67.811.17.45.57.911.38.76.710.28.716.512.410.223.617.314.49.67.76.811.57.116.113.111.97.18.136.419.613.2

Accounts Payable Current

us-gaap:AccountsPayableCurrent

us-gaap:AccountsPayableCurrent


Accounts
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value1815249.587161210108.5316.8434.2664.7314.3442.7293.9733.456.2963.2114.4453.2362.1043.2481.8131.2711.6551.9340.9630.5461.3022.0011.4051.752
Percentage of AccountsPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.22.63.61.33.82.72.13.33.72.81.63.12.83.34.23.19.94.14.62.91.62.32.91.84.94.71.91.02.011.16.14.4

Accrued Liabilities Current

us-gaap:AccruedLiabilitiesCurrent

us-gaap:AccruedLiabilitiesCurrent


Accrued
Period End2021-06-302020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value9153211011119.0586.2566.085.6025.7885.7437.4627.0025.7855.3114.2443.5682.7152.3272.2393.7622.8092.3353.3982.2972.686
Percentage of AccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.83.64.94.44.64.25.94.07.45.95.29.19.47.35.14.13.05.83.87.05.47.65.03.618.910.06.7

Contract With Customer Liability Current

us-gaap:ContractWithCustomerLiabilityCurrent

us-gaap:ContractWithCustomerLiabilityCurrent


Contract
Period End2021-06-302019-12-312019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value650.8240.6380.3710.4390.3180.2290.0
Percentage of ContractWithCustomerLiabilityCurrent100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets4.80.20.20.20.20.10.10.0

us-gaap:ContractWithCustomerLiabilityCurrent us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

mrtx:ZaiCollaborationAndLicenseAgreement


Contract
Period End2021-06-30
Value65
Percentage of ContractWithCustomerLiabilityCurrent100.0
Percentage of Assets4.8
Percentage of Assets mrtx:ZaiCollaborationAndLicenseAgreement0.0

Liabilities Current

us-gaap:LiabilitiesCurrent

us-gaap:LiabilitiesCurrent


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312013-12-312013-09-302013-06-302012-12-31
Value1807771675756483528252621181613131111151313109.7989.7697.0965.1115.3963841165.34
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets13.35.64.810.98.77.911.37.55.68.111.48.96.810.48.716.512.410.223.617.314.49.67.76.811.57.116.159.9230.972.913.4

Other Accrued Liabilities Current

us-gaap:OtherAccruedLiabilitiesCurrent

us-gaap:OtherAccruedLiabilitiesCurrent


Other
Period End2021-06-302021-03-312020-12-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-31
Value4626000.05143000.01712000.023000.02127000.019000.016000.040000.038000.036000.033000.031000.00
Percentage of OtherAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets0.30.40.10.02.60.00.00.10.00.00.00.00.0

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:OtherLiabilitiesNoncurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312018-12-312018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312013-06-302012-12-31
Value1428000.01139000.01962000.01541000.01251000.01174000.0999000.0600000.0400000.0314000.0133000.043000.021000.0011000.045000.0
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0
Percentage of Assets0.10.10.10.20.20.20.20.30.30.20.20.00.10.00.00.1

Operating Lease Liability Noncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent


Operating
Period End2021-06-302021-03-312020-12-31
Value444341
Percentage of OperatingLeaseLiabilityNoncurrent100.0100.0100.0
Percentage of Assets3.33.12.8

Lessee Operating Lease Liability Payments Due Year Two

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

mrtx:CurrentHeadquarters


Lessee
Period End2021-06-302021-03-312020-12-31
Value7844000.07844000.01681000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearTwo100.0100.0100.0
Percentage of Assets0.60.60.1
Percentage of Assets mrtx:CurrentHeadquarters0.00.00.0

Lessee Operating Lease Liability Payments Due Year Three

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

mrtx:CurrentHeadquarters


Lessee
Period End2021-06-302021-03-312020-12-31
Value8080000.08080000.07844000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearThree100.0100.0100.0
Percentage of Assets0.60.60.5
Percentage of Assets mrtx:CurrentHeadquarters0.00.00.0

Lessee Operating Lease Liability Payments Due Year Four

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

mrtx:CurrentHeadquarters


Lessee
Period End2021-06-302021-03-312020-12-31
Value8322000.08322000.08080000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFour100.0100.0100.0
Percentage of Assets0.60.60.5
Percentage of Assets mrtx:CurrentHeadquarters0.00.00.0

Lessee Operating Lease Liability Payments Due Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

mrtx:CurrentHeadquarters


Lessee
Period End2020-12-31
Value8322000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive100.0
Percentage of Assets0.6
Percentage of Assets mrtx:CurrentHeadquarters0.0

Lessee Operating Lease Liability Payments Due After Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

mrtx:CurrentHeadquarters


Lessee
Period End2020-12-31
Value68
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive100.0
Percentage of Assets4.6
Percentage of Assets mrtx:CurrentHeadquarters0.0

Operating Lease Liability

us-gaap:OperatingLeaseLiability us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:OperatingLeaseLiability

mrtx:CurrentHeadquarters


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value4443410.60.70.50.70.3
Percentage of OperatingLeaseLiability100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.33.12.80.10.10.10.20.1
Percentage of Assets mrtx:CurrentHeadquarters0.00.00.00.00.00.00.00.0

Lessee Operating Lease Liability Undiscounted Excess Amount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount


Lessee
Period End2021-06-30
Value49
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount100.0
Percentage of Assets3.7

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

mrtx:CurrentHeadquarters


Lessee
Period End2021-03-312020-12-31
Value5152
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount0.00.0
Percentage of Assets3.73.5
Percentage of Assets mrtx:CurrentHeadquarters0.00.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-312011-12-31
Value112812591360550605656382434472283201225246137143688299486582101118133546728354.8251325-23.5616.2373427
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets83.391.292.288.991.192.088.592.394.291.788.290.992.989.291.183.187.389.576.182.785.690.492.393.288.492.983.886.59.724.140.1-130.927.186.50.0

us-gaap:StockholdersEquity us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value9.6019.4569.75910119.7079.8899.8919.7889.6379.4799.4449.3459.1919.4799.5339.5589.5219.5079.528.945
Percentage of StockholdersEquity0.90.80.71.91.91.52.62.32.13.44.74.23.86.76.619.78.133.936.727.732.8
Percentage of Assets0.70.70.71.71.71.42.32.12.03.14.13.83.55.96.015.07.528.414.723.90.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value255125152481156915351505114411241108873751746740603594428415260214154132
Percentage of StockholdersEquity226.0199.8182.3284.9253.8229.4299.4258.8234.6308.2372.6331.6300.5438.2414.8887.0351.4928.7829.7448.1484.6
Percentage of Assets188.2182.2168.1253.2231.3211.0264.8238.9221.0282.5328.8301.3279.1390.8378.0675.4324.4778.4332.8387.50.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value0.0520.0510.050.0450.0450.0440.040.0390.0390.0360.0330.0330.0320.0290.0290.020.0190.0140.0130.010.006
Percentage of StockholdersEquity0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value-1432.348-1265.918-1130.238-1029.151-941.815-858.956-772.301-699.925-645.652-599.957-559.045-530.773-503.205-475.336-460.627-389.751-306.633-242.089-198.391-140.491-120.205
Percentage of StockholdersEquity-126.9-100.5-83.1-186.8-155.7-130.9-202.0-161.1-136.7-211.6-277.3-235.8-204.3-344.8-321.5-806.8-259.5-862.7-766.4-408.2-440.2
Percentage of Assets-105.7-91.7-76.6-166.0-141.9-120.4-178.7-148.7-128.8-193.9-244.7-214.3-189.8-307.6-292.9-614.3-239.5-723.1-307.4-353.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value52000.051000.050000.045000.045000.044000.040000.039000.039000.036000.033000.033000.032000.029000.029000.025000.025000.025000.020000.020000.020000.020000.019000.019000.016000.016000.014000.014000.014000.013000.013000.010000.010000.010000.0
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.00.0

Additional Paid In Capital

us-gaap:AdditionalPaidInCapital

us-gaap:AdditionalPaidInCapital


Additional
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value255125152481156915351505114411241108873751746740603594501499497428425423420415412314311260257218216214154154154
Percentage of AdditionalPaidInCapital100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets188.2182.2168.1253.2231.3211.0264.8238.9221.0282.5328.8301.3279.1390.8378.0610.9526.2449.2675.4538.0440.8373.9324.4287.1508.6431.6778.4624.3439.7383.8332.8855.9670.4387.5

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:RetainedEarningsAccumulatedDeficit


Retained
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value-1432300000.0-1265900000.0-1130200000.0-1029200000.0-941820000.0-858960000.0-772300000.0-699920000.0-645650000.0-599960000.0-559040000.0-530770000.0-503200000.0-475340000.0-460630000.0-442730000.0-426380000.0-408040000.0-389750000.0-370030000.0-350610000.0-328550000.0-306630000.0-288220000.0-269480000.0-254030000.0-242090000.0-231700000.0-223080000.0-212050000.0-198390000.0-187160000.0-157760000.0-140490000.0
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-105.7-91.7-76.6-166.0-141.9-120.4-178.7-148.7-128.8-193.9-244.7-214.3-189.8-307.6-292.9-539.5-448.9-368.4-614.3-467.5-365.2-292.0-239.5-200.6-435.5-351.9-723.1-560.9-449.2-376.6-307.4-1039.7-684.7-353.0

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value9.6019.4569.75910119.7079.8899.8919.7889.6379.4799.4449.3459.1919.4799.5149.5019.6049.5339.5849.6189.5859.5589.5199.5159.5259.5219.5289.5399.5169.5079.529.529.52
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.70.70.71.71.71.42.32.12.03.14.13.83.55.96.011.610.08.715.012.110.08.57.56.615.413.228.423.119.216.914.752.941.323.9

Stock Issued During Period Value New Issues

us-gaap:StockIssuedDuringPeriodValueNewIssues

us-gaap:StockIssuedDuringPeriodValueNewIssues


Stock
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-06-30
Value8790.00.03230.020.0219107130
Percentage of StockIssuedDuringPeriodValueNewIssues100.00.00.0100.0100.00.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.0

us-gaap:StockIssuedDuringPeriodValueNewIssues us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-06-30
Value8790.00.03230.020.001219107130
Percentage of StockIssuedDuringPeriodValueNewIssues100.00.00.0100.0100.00.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stock
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-06-30
Value0.0040.00.00.0040.0-0.0010.0030.0020.003
Percentage of StockIssuedDuringPeriodValueNewIssues0.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.0

Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value272421212021161512114.0583.8743.66
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value272421212021161512114.0583.8743.66
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-93367000.0-110420000.0-76421000.0-76763000.0-59343000.0-59004000.0-41902000.0-32874000.0-38468000.0-34482000.0-20795000.0-20172000.0-21181000.0-7948000.0-13766000.0-15091000.0-17617000.0-18232000.0-16123000.0-18298000.0-16644000.0-16952000.0-16030000.0-15870000.0-9039000.0-9775000.0-8587000.0-9617000.0-5746000.0-8798000.0-7712000.0-5195000.0-9208000.0-7340000.0-5188000.0-4183000.0
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-4476.9-671.90.0-22098.9-7966.2-3327.3-6666.9-2771.9-601.20.00.0-84.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value36-455.528-59.3464-22.447-122.227-6.939-128.066-5.927-35.208-63.68328-25.766-85.07811137.744-41.2118136.365-0.312-44.713177.776-31.1179.9145.9175.772.618-40.4043.0497.955-0.07-6.8851.52
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-3476.3561.60.0-45777.9-1319.2-12962.1-1027.2-2830.2-1841.10.00.0-898.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value7.8239.885889129.2733393.4731.0722211110.4622.1571325.89892.1490.071660.060.00.2662.3260.355950.335480.3510.10.1740.262540.0220.00.024
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.052131.8108.10.0127041.6660.3108.538454.48971.113.40.00.062.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value-48.783-556.059754-0.255-72.517157-45.368-159.86817741-84.01610
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.044178.6-2.20.059164.8-8625.1-16181.030760.33369.1-2428.90.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-93367000.0-110420000.0-76421000.0-76763000.0-59343000.0-59004000.0-41902000.0-32874000.0-38468000.0-34482000.0-20795000.0-20172000.0-21181000.0-7948000.0-13766000.0-15091000.0-17617000.0-18232000.0-16123000.0-18298000.0-16644000.0-16952000.0-16030000.0-15870000.0-9039000.0-9775000.0-8587000.0-9617000.0-5746000.0-8798000.0-7712000.0-5195000.0-9208000.0-7340000.0-5188000.0-4183000.0
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-4476.9-671.90.0-22098.9-7966.2-3327.3-6666.9-2771.9-601.20.00.0-84.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-166430000.0-135680000.0-101090000.0-87336000.0-82859000.0-86655000.0-72376000.0-54273000.0-45695000.0-40912000.0-28272000.0-27568000.0-27869000.0-14709000.0-17895000.0-16350000.0-18339000.0-17846000.0-19722000.0-19421000.0-22061000.0-21914000.0-18417000.0-18741000.0-15446000.0-11940000.0-10387000.0-8617000.0-11038000.0-13656000.0-11233000.0-29398000.0-8012000.0-4217000.0-6307000.0-5946000.0-4677000.0
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-5921.9-764.50.0-32455.1-13759.7-5493.2-7919.4-3288.7-817.30.00.0-155.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-166430000.0-135680000.0-101090000.0-87336000.0-82859000.0-86655000.0-72376000.0-54273000.0-45695000.0-40912000.0-27568000.0-27869000.0-14709000.0
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-5921.9-764.50.0-32455.1-13759.7-5493.2-7919.4-3288.70.00.0-155.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.0

Share Based Compensation

us-gaap:ShareBasedCompensation

us-gaap:ShareBasedCompensation


Share
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value272421212021161512114.2624.0583.8743.661.3181.4792.2231.7662.5382.762.2883.0382.3422.8042.7922.3162.2282.5911.2850.9460.7290.849-0.2170.4620.6110.746
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value36-455.528-59.3464-22.447-122.227-6.939-128.066-5.927-35.208-63.68328-25.766-85.07811137.744-41.2118136.365-0.312-44.713177.776-31.1179.9145.9175.772.618-40.4043.0497.955-0.07-6.8851.52
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.0-3476.3561.60.0-45777.9-1319.2-12962.1-1027.2-2830.2-1841.10.00.0-898.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value4030000.01107000.01506000.01436000.01201000.0224000.01332000.0151000.069000.0086000.036000.01000.0080000.00133000.018000.0045000.033000.0-1000.0279000.018000.066000.056000.0262000.02000.05000.043000.066000.090000.0161000.018000.0
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Payments To Acquire Investments

us-gaap:PaymentsToAcquireInvestments

us-gaap:PaymentsToAcquireInvestments


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value1446212067215323072245851271004.439481025.4558.67923633.008172721630.05.045351.53.0271.5184.423423.3346.3716123.906
Percentage of PaymentsToAcquireInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value7.8239.885889129.2733393.4731.0722211110.4622.1571325.89892.1490.071660.060.00.2662.3260.355950.335480.3510.10.1740.262540.0220.00.024
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.052131.8108.10.0127041.6660.3108.538454.48971.113.40.00.062.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

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

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice


Share
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value58.8244.119.5913.6716.5716.7114.011.1815.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Net

us-gaap:DeferredTaxAssetsNet

us-gaap:DeferredTaxAssetsNet


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value9260000.0122000.00000000
Percentage of DeferredTaxAssetsNet100.0100.00.00.00.00.00.00.00.0

Unrecognized Tax Benefits

us-gaap:UnrecognizedTaxBenefits us-gaap:IncomeTaxAuthority

us-gaap:UnrecognizedTaxBenefits

mrtx:CanadianFederal


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value7394000.04268000.02617000.01693000.01095000.0509000.042000.0129000.0159000.0157000.0
Percentage of UnrecognizedTaxBenefits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:CanadianProvincial


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value9652000.08648000.08010000.07556000.07333000.02274000.018000.023000.05000.03000.0
Percentage of UnrecognizedTaxBenefits130.5202.6306.1446.3669.7446.842.917.83.11.9

Deferred Tax Assets Valuation Allowance

us-gaap:DeferredTaxAssetsValuationAllowance

us-gaap:DeferredTaxAssetsValuationAllowance


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value270159106808456342113
Percentage of DeferredTaxAssetsValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:AdjustmentstoAdditionalPaidinCapitalDisgorgementofStockholdersShortSwingProfits

mrtx:AdjustmentstoAdditionalPaidinCapitalDisgorgementofStockholdersShortSwingProfits


Adjustmentsto
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value00041000.00001050000.0
Percentage of AdjustmentstoAdditionalPaidinCapitalDisgorgementofStockholdersShortSwingProfits0.00.00.0100.00.00.00.0100.0

mrtx:AdjustmentstoAdditionalPaidinCapitalDisgorgementofStockholdersShortSwingProfits us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Adjustmentsto
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value00041000.00001050000.0
Percentage of AdjustmentstoAdditionalPaidinCapitalDisgorgementofStockholdersShortSwingProfits0.00.00.0100.00.00.00.0100.0

mrtx:CollaborationArrangementResearchAndDevelopmentArrangementTransactionPrice us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

mrtx:CollaborationArrangementResearchAndDevelopmentArrangementTransactionPrice

mrtx:ZaiCollaborationAndLicenseAgreement


Collaboration
Period End2021-05-28
Value66
Percentage of CollaborationArrangementResearchAndDevelopmentArrangementTransactionPrice100.0

mrtx:CollaborationArrangementResearchAndDevelopmentArrangementUpFrontFeeReceived us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

mrtx:CollaborationArrangementResearchAndDevelopmentArrangementUpFrontFeeReceived

mrtx:ZaiCollaborationAndLicenseAgreement


Collaboration
Period End2021-05-28
Value65
Percentage of CollaborationArrangementResearchAndDevelopmentArrangementUpFrontFeeReceived100.0

mrtx:ConsiderationEarnedFromLicenseAgreementNoncash

mrtx:ConsiderationEarnedFromLicenseAgreementNoncash


Consideration
Period End2020-12-31
Value0.0
Percentage of ConsiderationEarnedFromLicenseAgreementNoncash0.0

mrtx:IncreaseDecreaseInOperatingLeaseLiability

mrtx:IncreaseDecreaseInOperatingLeaseLiability


Increase
Period End2021-03-312020-03-31
Value1270000.0-198000.0
Percentage of IncreaseDecreaseInOperatingLeaseLiability100.0100.0

mrtx:IncreaseDecreaseInRightOfUseAssets

mrtx:IncreaseDecreaseInRightOfUseAssets


Increase
Period End2021-06-302021-03-312020-06-302020-03-31
Value-573000.0-612000.0315000.0-188000.0
Percentage of IncreaseDecreaseInRightOfUseAssets100.0100.0100.0100.0

mrtx:PaymentsForTenantImprovementsNoncash

mrtx:PaymentsForTenantImprovementsNoncash


Payments
Period End2020-12-31
Value353000.0
Percentage of PaymentsForTenantImprovementsNoncash100.0

mrtx:ProceedsfromDisgorgementofStockholdersShortSwingProfits

mrtx:ProceedsfromDisgorgementofStockholdersShortSwingProfits


Proceedsfrom
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312019-01-312018-12-312018-09-30
Value00041000.00001050000.01100000.000
Percentage of ProceedsfromDisgorgementofStockholdersShortSwingProfits0.00.00.0100.00.00.00.0100.0100.00.00.0

mrtx:StockIssuedDuringPeriodValueWarrantsExercisedNoncash us-gaap:StatementEquityComponents

mrtx:StockIssuedDuringPeriodValueWarrantsExercisedNoncash

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312020-06-302019-12-312019-09-302019-06-302019-03-31
Value0-1000.0-1000.00-1000.00-1000.0
Percentage of StockIssuedDuringPeriodValueWarrantsExercisedNoncash0.0100.0100.00.0100.00.0100.0

us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-06-302019-12-312019-09-302019-06-302019-03-31
Value01000.01000.001000.001000.0
Percentage of StockIssuedDuringPeriodValueWarrantsExercisedNoncash0.0-100.0-100.00.0-100.00.0-100.0

us-gaap:CapitalExpendituresIncurredButNotYetPaid

us-gaap:CapitalExpendituresIncurredButNotYetPaid


Capital
Period End2021-03-312020-06-302020-03-312019-06-302019-03-312018-03-312017-03-312016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-31
Value439000.0-169000.0408000.000054000.000-197000.0197000.030000.0-21000.042000.0
Percentage of CapitalExpendituresIncurredButNotYetPaid100.0100.0100.00.00.00.0100.00.00.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiabilityRevenueRecognized us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

us-gaap:ContractWithCustomerLiabilityRevenueRecognized

mrtx:BeiGeneCollaborationandLicenseAgreement


Contract
Period End2020-12-312020-09-302020-06-302020-03-31
Value143000.00029000.0
Percentage of ContractWithCustomerLiabilityRevenueRecognized100.00.00.0100.0

us-gaap:Depreciation

us-gaap:Depreciation


Depreciation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value411000.0294000.0206000.0200000.0100000.0126000.093000.057000.055000.044000.044000.00100000.041000.046000.0055000.045000.041000.039000.042000.058000.059000.053000.056000.044000.045000.039000.038000.078000.066000.041000.042000.022000.025000.030000.0
Percentage of Depreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1

us-gaap:FairValueInputsLevel3


Fair
Period End2021-06-302021-03-312020-12-31
Value2729000.03953000.0-4229000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases

us-gaap:FairValueInputsLevel3


Fair
Period End2020-12-31
Value0.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases0.0

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value1044.3715.9378.5031.8946.909137.2343.168-1.0714.2743.7612.142.7451.991-0.2150.423-3.541.362-0.1392.9641.009-0.0342.6672.219-0.4820.04-0.5381.953-1.304-1.3512.039-1.2230.4670.4331.374
Percentage of IncreaseDecreaseInAccountsPayableAndAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInContractWithCustomerLiability us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:ResearchAndDevelopmentArrangementContractToPerformForOthersByType

us-gaap:IncreaseDecreaseInContractWithCustomerLiability

mrtx:BeiGeneCollaborationandLicenseAgreement, mrtx:ManufacturingSupplyServices


Increase
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-1700000.000-300000.0-500000.0-1000000.0-600000.0-1200000.0
Percentage of IncreaseDecreaseInContractWithCustomerLiability100.00.00.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherCurrentAssets

us-gaap:IncreaseDecreaseInOtherCurrentAssets


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value652.81-2.8058.014-1.1290.1-1.0790.2534.7851.5280.3850.073-1.008-0.5021.357-0.0022.758-0.7040.3170.778-0.506-0.8430.051.009-1.15-0.1880.7160.894-0.9180.517-0.313-0.2770.565-0.315-0.090.395
Percentage of IncreaseDecreaseInOtherCurrentAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-30
Value401000.08149000.01999000.0434000.078000.0331000.0502000.0-109000.02753000.01229000.0155000.020000.0159000.025000.00-895000.0-710000.0739000.0395000.001713000.0-38000.00416000.024000.000
Percentage of IncreaseDecreaseInOtherNoncurrentAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.00.0100.0100.00.0100.0100.00.00.0

us-gaap:InvestmentIncomeNetAmortizationOfDiscountAndPremium

us-gaap:InvestmentIncomeNetAmortizationOfDiscountAndPremium


Investment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value-1224000.0-1001000.0-203000.014000.0343000.0520000.0603000.0854000.01047000.0917000.0563000.0381000.0214000.0162000.034000.054000.0107000.071000.0-1000.019000.0-11000.0-14000.0
Percentage of InvestmentIncomeNetAmortizationOfDiscountAndPremium100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingLeaseExpense us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:OperatingLeaseExpense

mrtx:CurrentHeadquarters


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value2000000.02000000.0296000.0004000.0
Percentage of OperatingLeaseExpense100.0100.0100.00.00.0100.0

us-gaap:OperatingLeaseExpense us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty, us-gaap:PropertyPlantAndEquipmentByType

mrtx:CurrentHeadquarters, us-gaap:Building


Operating
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value024100.00024100.0
Percentage of OperatingLeaseExpense0.01.20.00.0602.5

mrtx:FutureHeadquarters, us-gaap:Building


Operating
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value0600000.00-3200000.03800000.0
Percentage of OperatingLeaseExpense0.030.00.00.095000.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value145000.0-303000.0-698000.0-827000.01577000.0-182000.0-2000.0103000.0151000.0158000.035000.099000.0154000.0-288000.0-35000.013000.0-104000.071000.0-51000.0-34000.033000.027000.035000.06000.0-9000.05000.0-8000.0-12000.024000.010000.0-13000.0000
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value145000.0-303000.0-698000.0-827000.01577000.0-182000.0-2000.0103000.0151000.0158000.099000.0154000.0-288000.0
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromIssuanceOfCommonStock


Proceeds
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-02-282015-03-312014-12-312014-09-302014-06-302014-03-31
Value8790.00.03230.020.02191070.00.0031300.0860.00.0660.00.00.00.00.004940.048480.00.00.00.0
Percentage of ProceedsFromIssuanceOfCommonStock100.00.00.0100.0100.00.0100.0100.00.0100.0100.00.0100.00.00.0100.00.00.00.00.0100.0100.00.0100.0100.00.00.00.00.0

us-gaap:ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions

us-gaap:ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions


Proceeds
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value6.6099.885128.749151.072
Percentage of ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleMaturityAndCollectionsOfInvestments

us-gaap:ProceedsFromSaleMaturityAndCollectionsOfInvestments


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value1851671481381321086611779923633221716223022213134211917134.88119.07.557.0432.2516.43214165.3535.458
Percentage of ProceedsFromSaleMaturityAndCollectionsOfInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromStockOptionsExercised

us-gaap:ProceedsFromStockOptionsExercised


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-11-302017-12-312017-09-302017-01-312016-12-312016-09-302015-09-302015-06-302015-03-312014-09-302014-06-302014-03-31
Value6.69.99.6128.7153.11.11.62.70.22.21.55.9864.560.04661.90.040.1420.0850.2450.10.1740.262
Percentage of ProceedsFromStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromStockPlans

us-gaap:ProceedsFromStockPlans


Proceeds
Period End2020-09-302019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302016-09-30
Value00-727000.01050000.00202000.0000
Percentage of ProceedsFromStockPlans0.00.0100.0100.00.0100.00.00.00.0

us-gaap:SaleOfStockConsiderationReceivedOnTransaction

us-gaap:SaleOfStockConsiderationReceivedOnTransaction


Sale
Period End2020-10-312020-01-312019-06-302019-01-312018-06-30
Value879324219107130
Percentage of SaleOfStockConsiderationReceivedOnTransaction100.0100.0100.0100.0100.0

us-gaap:SaleOfStockConsiderationReceivedOnTransaction us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType

us-gaap:CommonClassA, us-gaap:SubsequentEvent


Sale
Period End2020-10-31
Value879
Percentage of SaleOfStockConsiderationReceivedOnTransaction100.0

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan


Stock
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value6.6099.885128.749151.0721.632
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value6.6089.885128.749151.0721.632
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommonStock


Stock
Period End2021-06-30
Value0.001
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan0.0

us-gaap:StockIssuedDuringPeriodValueEmployeeStockPurchasePlan

us-gaap:StockIssuedDuringPeriodValueEmployeeStockPurchasePlan


Stock
Period End2021-06-302020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302018-06-30
Value1214000.0682000.00524000.0352000.00323000.0202000.0
Percentage of StockIssuedDuringPeriodValueEmployeeStockPurchasePlan100.0100.00.0100.0100.00.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueEmployeeStockPurchasePlan us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302018-06-30
Value1214000.0682000.00524000.0352000.00323000.0202000.0
Percentage of StockIssuedDuringPeriodValueEmployeeStockPurchasePlan100.0100.00.0100.0100.00.0100.0100.0

us-gaap:UnrealizedGainLossOnInvestments

us-gaap:UnrealizedGainLossOnInvestments


Unrealized
Period End2021-06-302021-03-312020-12-31
Value-2729000.0-3953000.04229000.0
Percentage of UnrealizedGainLossOnInvestments100.0100.0100.0

mrtx:AccruedClinicalExpense

mrtx:AccruedClinicalExpense


Accrued
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value3024323522352114111010
Percentage of AccruedClinicalExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:AccruedDevelopmentExpense

mrtx:AccruedDevelopmentExpense


Accrued
Period End2021-06-302021-03-312020-12-31
Value7660000.04537000.05439000.0
Percentage of AccruedDevelopmentExpense100.0100.0100.0

mrtx:AccruedDevelopmentandOtherExpense

mrtx:AccruedDevelopmentandOtherExpense


Accrued
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value7151000.07414000.04743000.06171000.02510000.02613000.01814000.01454000.01243000.0
Percentage of AccruedDevelopmentandOtherExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:AccruedManufacturingExpense

mrtx:AccruedManufacturingExpense


Accrued
Period End2021-06-302021-03-312020-12-31
Value361513
Percentage of AccruedManufacturingExpense100.0100.0100.0

mrtx:CollaborationArrangementResearchAndDevelopmentArrangementContractToPerformForOthersCompensationExpectedToBeEarned us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:ResearchAndDevelopmentArrangementContractToPerformForOthersByType

mrtx:CollaborationArrangementResearchAndDevelopmentArrangementContractToPerformForOthersCompensationExpectedToBeEarned

mrtx:BeiGeneCollaborationandLicenseAgreement, mrtx:MilestonePayments


Collaboration
Period End2021-06-30
Value5.0
Percentage of CollaborationArrangementResearchAndDevelopmentArrangementContractToPerformForOthersCompensationExpectedToBeEarned100.0

mrtx:ZaiCollaborationAndLicenseAgreement, mrtx:DevelopmentAndRegulatoryBasedMilestonePayments


Collaboration
Period End2021-05-28
Value93
Percentage of CollaborationArrangementResearchAndDevelopmentArrangementContractToPerformForOthersCompensationExpectedToBeEarned0.0

mrtx:ZaiCollaborationAndLicenseAgreement, mrtx:SalesMilestonePayments


Collaboration
Period End2021-05-28
Value180
Percentage of CollaborationArrangementResearchAndDevelopmentArrangementContractToPerformForOthersCompensationExpectedToBeEarned0.0

mrtx:CollaborativeArrangementCollaborationReceivable

mrtx:CollaborativeArrangementCollaborationReceivable


Collaborative
Period End2021-06-30
Value65
Percentage of CollaborativeArrangementCollaborationReceivable100.0

mrtx:ContractwithCustomerLiabilityCurrentandOtherLiabilitiesCurrent

mrtx:ContractwithCustomerLiabilityCurrentandOtherLiabilitiesCurrent


Contractwith
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value57530.6970.8520.5970.824
Percentage of ContractwithCustomerLiabilityCurrentandOtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0

mrtx:DeferredTaxAssetsLeaseLiability

mrtx:DeferredTaxAssetsLeaseLiability


Deferred
Period End2020-12-312019-12-312018-12-31
Value8800000.0137000.00
Percentage of DeferredTaxAssetsLeaseLiability100.0100.00.0

mrtx:DeferredTaxAssetsScientificResearchAndExperimentalDevelopmentExpenditures

mrtx:DeferredTaxAssetsScientificResearchAndExperimentalDevelopmentExpenditures


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value5471000.05471000.05467000.05467000.05531000.05552000.05715000.05766000.04245000.0
Percentage of DeferredTaxAssetsScientificResearchAndExperimentalDevelopmentExpenditures100.0100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:DeferredTaxAssetsTangibleAndIntangibleDepreciableAssets

mrtx:DeferredTaxAssetsTangibleAndIntangibleDepreciableAssets


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value326.9788.123170.990.1990.1850.8740.853
Percentage of DeferredTaxAssetsTangibleAndIntangibleDepreciableAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:DeferredTaxLiabilitiesOperatingRightofUseAsset

mrtx:DeferredTaxLiabilitiesOperatingRightofUseAsset


Deferred
Period End2020-12-312019-12-312018-12-31
Value8377000.0122000.00
Percentage of DeferredTaxLiabilitiesOperatingRightofUseAsset100.0100.00.0

mrtx:DepositsPaidForResearchAndDevelopment

mrtx:DepositsPaidForResearchAndDevelopment


Deposits
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-31
Value17168.66.05.45.65.15.25.32.61.31.21.11.01.02.12.12.23.33.12.42.02.02.00.3
Percentage of DepositsPaidForResearchAndDevelopment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:LicenseAgreementOneTimeNonCashPayment us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:FairValueByFairValueHierarchyLevel

mrtx:LicenseAgreementOneTimeNonCashPayment

mrtx:ORICPharmaceuticalsAgreement, us-gaap:FairValueInputsLevel3


License
Period End2020-08-03
Value11
Percentage of LicenseAgreementOneTimeNonCashPayment100.0

mrtx:SaleofStockAggregateOfferingPrice

mrtx:SaleofStockAggregateOfferingPrice


Saleof
Period End2020-07-02
Value200
Percentage of SaleofStockAggregateOfferingPrice100.0

mrtx:SecurityDepositsAndOtherReceivables

mrtx:SecurityDepositsAndOtherReceivables


Security
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-31
Value4659000.04576000.03075000.05914000.01471000.01613000.02119000.02247000.03246000.02985000.01841000.01287000.01071000.01325000.01600000.0771000.0853000.0733000.0759000.0836000.0516000.0536000.0551000.0482000.0634000.0530000.0622000.0
Percentage of SecurityDepositsAndOtherReceivables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsPayableCurrentAndNoncurrent

us-gaap:AccountsPayableCurrentAndNoncurrent


Accounts
Period End2021-06-302021-03-312020-12-31
Value231918
Percentage of AccountsPayableCurrentAndNoncurrent100.0100.0100.0

us-gaap:AccruedLiabilitiesCurrentAndNoncurrent

us-gaap:AccruedLiabilitiesCurrentAndNoncurrent


Accrued
Period End2021-06-302021-03-312020-12-31
Value915753
Percentage of AccruedLiabilitiesCurrentAndNoncurrent100.0100.0100.0

us-gaap:AssetsFairValueDisclosure

us-gaap:AssetsFairValueDisclosure


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value120512981405590645695415454300222
Percentage of AssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetsFairValueDisclosure us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value339408935184195229831249336
Percentage of AssetsFairValueDisclosure28.131.466.531.330.233.020.027.531.116.4

us-gaap:FairValueInputsLevel2


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value857878454394450465332329207186
Percentage of AssetsFairValueDisclosure71.167.732.466.869.867.080.072.568.983.6

us-gaap:FairValueInputsLevel3


Assets
Period End2021-06-302021-03-312020-12-312020-09-302019-03-312018-12-31
Value8.9471115110.00.0
Percentage of AssetsFairValueDisclosure0.70.91.11.90.00.0

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value167000.0140000.0265000.0940000.01765000.0878000.0375000.0380000.0124000.026000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax us-gaap:FinancialInstrument

us-gaap:CommercialPaper


Available
Period End2020-12-312019-12-312018-12-312017-12-31
Value58000.074000.000
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax21.919.70.00.0

us-gaap:CommercialPaperNotIncludedWithCashAndCashEquivalents


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value99000.037000.058000.0296000.0594000.0440000.074000.067000.044000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax59.326.421.931.533.750.119.717.635.50.0

us-gaap:CorporateDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value29000.045000.0160000.0576000.01044000.0162000.0233000.0271000.075000.026000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax17.432.160.461.359.218.562.171.360.5100.00.0

us-gaap:USGovernmentAgenciesDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value29000.048000.037000.038000.075000.0122000.041000.021000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax17.434.314.04.04.213.910.95.5

us-gaap:USTreasuryBillSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value10000.010000.010000.030000.052000.0154000.027000.021000.05000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax6.07.13.83.22.917.57.25.54.00.0

us-gaap:USTreasurySecurities


Available
Period End2020-12-312019-12-312018-12-31
Value10000.027000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax3.87.20.0

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value86000.0204000.026000.03000.03000.0696000.06000.013000.05000.067000.042000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax us-gaap:FinancialInstrument

us-gaap:CommercialPaper


Available
Period End2020-12-312019-12-312018-12-312017-12-31
Value18000.0024000.019000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax69.20.035.845.2

us-gaap:CommercialPaperNotIncludedWithCashAndCashEquivalents


Available
Period End2021-03-312020-12-312020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value19000.018000.01000.04000.0001000.024000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax9.369.233.30.60.00.020.035.8

us-gaap:CorporateDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value79000.0181000.04000.00692000.01000.03000.04000.043000.023000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax91.988.715.40.099.416.723.180.064.254.8

us-gaap:SovereignDebtSecurities


Available
Period End2021-06-302021-03-312019-03-31
Value4000.04000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax4.72.00.0

us-gaap:USGovernmentAgenciesDebtSecurities


Available
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value1000.03000.01000.004000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax3.8100.033.30.066.70.0

us-gaap:USTreasuryBillSecurities


Available
Period End2021-06-302020-12-312020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value3000.03000.01000.001000.010000.000
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax3.511.533.30.016.776.90.00.0

us-gaap:USTreasurySecurities


Available
Period End2020-12-312019-12-312018-12-31
Value3000.01000.00
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax11.516.70.0

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value91595750444651249036836122619043
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis us-gaap:FinancialInstrument

us-gaap:CommercialPaper


Available
Period End2020-12-312019-12-312018-12-312017-12-31
Value2401207418
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis47.732.839.143.8

us-gaap:CommercialPaperNotIncludedWithCashAndCashEquivalents


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value53855324015423319212011011474
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis58.857.847.734.745.539.332.830.650.539.1

us-gaap:CorporateDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value1921821301591772281601809111124
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis21.119.125.935.734.646.543.549.940.358.956.2

us-gaap:SovereignDebtSecurities


Available
Period End2021-06-302021-03-312019-03-31
Value9.0729.1131.988
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis1.01.00.9

us-gaap:USGovernmentAgenciesDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value116133837938445037
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis12.713.916.517.77.59.113.810.4

us-gaap:USTreasuryBillSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value5878495363253632183.771
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis6.48.29.811.912.45.19.99.18.32.0

us-gaap:USTreasurySecurities


Available
Period End2020-12-312019-12-312018-12-31
Value49363.771
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis9.89.92.0

us-gaap:AvailableForSaleSecuritiesDebtSecurities

us-gaap:AvailableForSaleSecuritiesDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value91595750444751449036836222619043
Percentage of AvailableForSaleSecuritiesDebtSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AvailableForSaleSecuritiesDebtSecurities us-gaap:FinancialInstrument

us-gaap:CommercialPaper


Available
Period End2020-12-312019-12-312018-12-312017-12-31
Value2401207418
Percentage of AvailableForSaleSecuritiesDebtSecurities47.732.839.143.8

us-gaap:CommercialPaperNotIncludedWithCashAndCashEquivalents


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value53855324015523319312011011474
Percentage of AvailableForSaleSecuritiesDebtSecurities58.857.847.734.645.539.332.830.650.539.1

us-gaap:CorporateDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-312017-12-31
Value1921821301601782271601809111124
Percentage of AvailableForSaleSecuritiesDebtSecurities21.019.126.035.834.746.443.549.940.358.956.2

us-gaap:SovereignDebtSecurities


Available
Period End2021-06-302021-03-312019-03-31
Value9.0689.1091.988
Percentage of AvailableForSaleSecuritiesDebtSecurities1.01.00.9

us-gaap:USGovernmentAgenciesDebtSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value116133837938445037
Percentage of AvailableForSaleSecuritiesDebtSecurities12.713.916.517.77.59.113.810.4

us-gaap:USTreasuryBillSecurities


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value5878495363253632183.771
Percentage of AvailableForSaleSecuritiesDebtSecurities6.48.29.811.912.35.19.99.18.32.0

us-gaap:USTreasurySecurities


Available
Period End2020-12-312019-12-312018-12-31
Value49363.771
Percentage of AvailableForSaleSecuritiesDebtSecurities9.89.92.0

us-gaap:CashAndCashEquivalentsFairValueDisclosure

us-gaap:CashAndCashEquivalentsFairValueDisclosure


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value28032988513113120446917432
Percentage of CashAndCashEquivalentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CashAndCashEquivalentsFairValueDisclosure us-gaap:CashAndCashEquivalents

us-gaap:Cash


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value21342018125.4880.6623.0781.9093.731
Percentage of CashAndCashEquivalentsFairValueDisclosure7.710.52.314.39.32.71.43.32.611.4

us-gaap:MoneyMarketFunds


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value25829486511211919945887228
Percentage of CashAndCashEquivalentsFairValueDisclosure92.389.597.785.790.797.398.696.797.488.6

us-gaap:CashAndCashEquivalentsFairValueDisclosure us-gaap:CashAndCashEquivalents, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:Cash, us-gaap:FairValueInputsLevel1


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value21342018125.4880.6623.0781.9093.731
Percentage of CashAndCashEquivalentsFairValueDisclosure7.710.52.314.39.32.71.43.32.611.4

us-gaap:MoneyMarketFunds, us-gaap:FairValueInputsLevel1


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value25829486511211919945887228
Percentage of CashAndCashEquivalentsFairValueDisclosure92.389.597.785.790.797.398.696.797.488.6

us-gaap:CashAndCashEquivalentsFairValueDisclosure us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value28032988513113120446917432
Percentage of CashAndCashEquivalentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ClassOfWarrantOrRightOutstanding

us-gaap:ClassOfWarrantOrRightOutstanding


Class
Period End2020-12-312020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-11-302017-01-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value8.2296329.0928739.6928799.6928799.692879101011111111114.1379997.2582631.4283831.4283832.2731432.4524392.4657132.4657132.4693332.5293332.539677
Percentage of ClassOfWarrantOrRightOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ClassOfWarrantOrRightOutstanding us-gaap:ClassOfWarrantOrRight, us-gaap:SubsidiarySaleOfStock

mrtx:ClassofWarrantsIssuedJune112018, us-gaap:PrivatePlacement


Class
Period End2020-12-312019-12-31
Value0.3584150.42165
Percentage of ClassOfWarrantOrRightOutstanding4.44.4

us-gaap:ContractWithCustomerAssetGross us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:ResearchAndDevelopmentArrangementContractToPerformForOthersByType

us-gaap:ContractWithCustomerAssetGross

mrtx:BeiGeneCollaborationandLicenseAgreement, mrtx:ManufacturingSupplyServices


Contract
Period End2020-12-312019-12-31
Value1300000.0400000.0
Percentage of ContractWithCustomerAssetGross100.0100.0

us-gaap:ContractWithCustomerLiability us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject

us-gaap:ContractWithCustomerLiability

mrtx:BeiGeneCollaborationandLicenseAgreement


Contract
Period End2020-09-302020-06-302020-03-312019-12-31
Value143000.0143000.0143000.0172000.0
Percentage of ContractWithCustomerLiability100.0100.0100.0100.0

us-gaap:DeferredTaxAssetsCapitalLossCarryforwards

us-gaap:DeferredTaxAssetsCapitalLossCarryforwards


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value114000.0178000.0178000.083000.051000.0102000.00
Percentage of DeferredTaxAssetsCapitalLossCarryforwards100.0100.0100.0100.0100.0100.00.0

us-gaap:DeferredTaxAssetsGross

us-gaap:DeferredTaxAssetsGross


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value279159106808456342113
Percentage of DeferredTaxAssetsGross100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxAssetsOperatingLossCarryforwards

us-gaap:DeferredTaxAssetsOperatingLossCarryforwards


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value1821167444664223136.883
Percentage of DeferredTaxAssetsOperatingLossCarryforwards100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxAssetsTaxCreditCarryforwardsResearch

us-gaap:DeferredTaxAssetsTaxCreditCarryforwardsResearch


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value2817107.0164.2662.4110.2660.0
Percentage of DeferredTaxAssetsTaxCreditCarryforwardsResearch100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value19126.5154.9766.6354.4292.360.0
Percentage of DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value2510000.0934000.01020000.0611000.0853000.0725000.0554000.093000.030000.0
Percentage of DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxLiabilitiesInvestments

us-gaap:DeferredTaxLiabilitiesInvestments


Deferred
Period End2020-12-31
Value883000.0
Percentage of DeferredTaxLiabilitiesInvestments100.0

us-gaap:EmployeeRelatedLiabilitiesCurrent

us-gaap:EmployeeRelatedLiabilitiesCurrent


Employee
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value127.689138.05.0814.3657.9154.8213.4192.4385.8473.3652.521.9723.0212.6442.1432.0282.9232.952.3071.7622.3522.2481.7021.1251.4141.2151.190.6281.6081.1560.8140.834
Percentage of EmployeeRelatedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized


Employee
Period End2020-12-31
Value61
Percentage of EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized100.0

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized us-gaap:AwardType

us-gaap:RestrictedStockUnitsRSU


Employee
Period End2020-12-31
Value31
Percentage of EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized51.1

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue

us-gaap:FairValueInputsLevel3


Fair
Period End2021-06-302021-03-312020-12-312020-09-30
Value8.947111511
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue100.0100.0100.0100.0

us-gaap:InterestReceivableCurrent

us-gaap:InterestReceivableCurrent


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312013-09-302013-06-302012-12-31
Value2123000.01838000.02304000.01535000.01813000.01959000.01566000.01618000.0840000.0792000.0768000.0472000.0790000.0403000.0237000.0157000.0239000.0157000.0183000.0134000.0282000.0166000.0237000.0233000.0179000.0283000.096000.026000.042000.082000.0
Percentage of InterestReceivableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentsFairValueDisclosure

us-gaap:InvestmentsFairValueDisclosure


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value915957504447514490368362226190
Percentage of InvestmentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentsFairValueDisclosure us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value5878495363253632183.771
Percentage of InvestmentsFairValueDisclosure6.48.29.811.912.35.19.99.18.32.0

us-gaap:FairValueInputsLevel2


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value857878454394450465332329207186
Percentage of InvestmentsFairValueDisclosure93.691.890.288.187.794.990.190.991.798.0

us-gaap:InvestmentsFairValueDisclosure us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FinancialInstrument

us-gaap:FairValueInputsLevel1, us-gaap:USTreasuryBillSecurities


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value5878495363253632183.771
Percentage of InvestmentsFairValueDisclosure6.48.29.811.912.35.19.99.18.32.0

us-gaap:FairValueInputsLevel2, us-gaap:CommercialPaperNotIncludedWithCashAndCashEquivalents


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value53855324015523319312011011474
Percentage of InvestmentsFairValueDisclosure58.857.847.734.645.539.332.830.650.539.1

us-gaap:FairValueInputsLevel2, us-gaap:CorporateDebtSecurities


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value19218213016017822716018091111
Percentage of InvestmentsFairValueDisclosure21.019.126.035.834.746.443.549.940.358.9

us-gaap:FairValueInputsLevel2, us-gaap:SovereignDebtSecurities


Investments
Period End2021-06-302021-03-312019-03-31
Value9.0689.1091.988
Percentage of InvestmentsFairValueDisclosure1.01.00.9

us-gaap:FairValueInputsLevel2, us-gaap:USGovernmentAgenciesDebtSecurities


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value116133837938445037
Percentage of InvestmentsFairValueDisclosure12.713.916.517.77.59.113.810.4

us-gaap:FairValueInputsLevel3, us-gaap:OtherLongTermInvestments


Investments
Period End2021-06-302021-03-312020-12-312020-09-30
Value8.947111511
Percentage of InvestmentsFairValueDisclosure1.01.23.12.5

us-gaap:InvestmentsFairValueDisclosure us-gaap:FinancialInstrument

us-gaap:CommercialPaperNotIncludedWithCashAndCashEquivalents


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value53855324015523319312011011474
Percentage of InvestmentsFairValueDisclosure58.857.847.734.645.539.332.830.650.539.1

us-gaap:CorporateDebtSecurities


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value19218213016017822716018091111
Percentage of InvestmentsFairValueDisclosure21.019.126.035.834.746.443.549.940.358.9

us-gaap:OtherLongTermInvestments


Investments
Period End2021-06-302021-03-312020-12-312020-09-30
Value8.947111511
Percentage of InvestmentsFairValueDisclosure1.01.23.12.5

us-gaap:SovereignDebtSecurities


Investments
Period End2021-06-302021-03-312019-03-31
Value9.0689.1091.988
Percentage of InvestmentsFairValueDisclosure1.01.00.9

us-gaap:USGovernmentAgenciesDebtSecurities


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value116133837938445037
Percentage of InvestmentsFairValueDisclosure12.713.916.517.77.59.113.810.4

us-gaap:USTreasuryBillSecurities


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-03-312018-12-31
Value5878495363253632183.771
Percentage of InvestmentsFairValueDisclosure6.48.29.811.912.35.19.99.18.32.0

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths

mrtx:CurrentHeadquarters


Lessee
Period End2021-06-302021-03-312020-09-30
Value1681000.01681000.0100000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths100.0100.0100.0

us-gaap:LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear

mrtx:CurrentHeadquarters


Lessee
Period End2020-09-30
Value100000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear100.0

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent

mrtx:CurrentHeadquarters


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value12.012.012.012.00.120.120.120.12
Percentage of OperatingLeaseWeightedAverageDiscountRatePercent100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingLossCarryforwards mrtx:ExpirationPeriod, us-gaap:IncomeTaxAuthority

us-gaap:OperatingLossCarryforwards

mrtx:ExpirationPeriod2030, mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value4.834.835.9075.9075.9075.9075.9075.907
Percentage of OperatingLossCarryforwards100.0100.0100.0100.0100.0100.0100.0100.0

mrtx:ExpirationPeriod2030, mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value4.9074.9075.9855.9855.9855.9855.9855.984
Percentage of OperatingLossCarryforwards101.6101.6101.3101.3101.3101.3101.3101.3

mrtx:ExpirationPeriod2032, mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value1313131313131312
Percentage of OperatingLossCarryforwards275.5275.5225.3225.3225.3225.4225.4209.4

mrtx:ExpirationPeriod2032, mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value1212121212121212
Percentage of OperatingLossCarryforwards257.4257.4210.5210.5210.5210.5210.5211.5

mrtx:ExpirationPeriod2033, mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value1818181818181818
Percentage of OperatingLossCarryforwards385.6385.6315.3315.3315.3315.3315.3316.9

mrtx:ExpirationPeriod2033, mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value1919191919191919
Percentage of OperatingLossCarryforwards401.3401.3328.2328.2328.2328.2328.2329.6

mrtx:ExpirationPeriod2033, us-gaap:InternalRevenueServiceIRS


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value2.2252.2252.2252.2253.2613.2363.2612.838
Percentage of OperatingLossCarryforwards46.146.137.737.755.254.855.248.0

mrtx:ExpirationPeriod2033, us-gaap:StateAndLocalJurisdiction


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value2.2322.2322.2322.2322.2862.2862.2862.919
Percentage of OperatingLossCarryforwards46.246.237.837.838.738.738.749.4

mrtx:ExpirationPeriod2034, mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value32323232323226
Percentage of OperatingLossCarryforwards670.8670.8548.5548.5548.5548.5452.7

mrtx:ExpirationPeriod2034, mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value31313131313126
Percentage of OperatingLossCarryforwards658.6658.6538.5538.5538.5538.5442.7

mrtx:ExpirationPeriod2034, us-gaap:InternalRevenueServiceIRS


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value7.2767.2767.2767.2767.267.2767.012
Percentage of OperatingLossCarryforwards150.6150.6123.2123.2122.9123.2118.7

mrtx:ExpirationPeriod2034, us-gaap:StateAndLocalJurisdiction


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value2222222222227.185
Percentage of OperatingLossCarryforwards458.8458.8375.2375.2375.2375.2121.6

mrtx:ExpirationPeriod2035, mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value1.0841.0841.0841.0841.0841.117
Percentage of OperatingLossCarryforwards22.422.418.418.418.418.9

mrtx:ExpirationPeriod2035, mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value1.0841.0841.0841.0841.0841.116
Percentage of OperatingLossCarryforwards22.422.418.418.418.418.9

mrtx:ExpirationPeriod2035, us-gaap:InternalRevenueServiceIRS


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value535353535353
Percentage of OperatingLossCarryforwards1104.71104.7903.3903.3903.1903.0

mrtx:ExpirationPeriod2035, us-gaap:StateAndLocalJurisdiction


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value52525252520.0
Percentage of OperatingLossCarryforwards1096.31096.3896.4896.4895.20.0

mrtx:ExpirationPeriod2036, us-gaap:InternalRevenueServiceIRS


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value2323232369
Percentage of OperatingLossCarryforwards484.0484.0395.8395.81176.7

mrtx:ExpirationPeriod2037, mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-312018-12-312017-12-31
Value0.6970.6970.6971.408
Percentage of OperatingLossCarryforwards14.414.411.823.8

mrtx:ExpirationPeriod2037, mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-312018-12-312017-12-31
Value0.6970.6970.6971.408
Percentage of OperatingLossCarryforwards14.414.411.823.8

mrtx:ExpirationPeriod2037, us-gaap:InternalRevenueServiceIRS


Operating
Period End2020-12-312019-12-312018-12-312017-12-31
Value65656524
Percentage of OperatingLossCarryforwards1356.31356.31109.0407.0

mrtx:ExpirationPeriod2038, us-gaap:StateAndLocalJurisdiction


Operating
Period End2020-12-312019-12-312018-12-31
Value3.8173.8170.0
Percentage of OperatingLossCarryforwards79.079.00.0

mrtx:ExpirationPeriod2039, mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-31
Value0.2420.274
Percentage of OperatingLossCarryforwards5.05.7

mrtx:ExpirationPeriod2039, mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-31
Value0.2420.274
Percentage of OperatingLossCarryforwards5.05.7

mrtx:ExpirationPeriod2040, mrtx:CanadianFederal


Operating
Period End2020-12-31
Value0.273
Percentage of OperatingLossCarryforwards5.7

mrtx:ExpirationPeriod2040, mrtx:CanadianProvincial


Operating
Period End2020-12-31
Value0.273
Percentage of OperatingLossCarryforwards5.7

mrtx:ExpirationPeriod2040, us-gaap:StateAndLocalJurisdiction


Operating
Period End2020-12-31
Value193
Percentage of OperatingLossCarryforwards3999.2

mrtx:NoExpiration, us-gaap:InternalRevenueServiceIRS


Operating
Period End2020-12-312019-12-312018-12-31
Value551300102
Percentage of OperatingLossCarryforwards11410.66227.01741.4

us-gaap:OperatingLossCarryforwards us-gaap:IncomeTaxAuthority

mrtx:CanadianFederal


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value797979807978714425
Percentage of OperatingLossCarryforwards1641.81637.71352.01363.91340.11327.61212.8745.80.0

mrtx:CanadianProvincial


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value787879797877714525
Percentage of OperatingLossCarryforwards1629.41623.21341.51353.41329.61317.01202.3762.00.0

us-gaap:InternalRevenueServiceIRS


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value70245225411013363102.8380.0
Percentage of OperatingLossCarryforwards14552.89368.54310.31867.02257.91081.0173.948.00.0

us-gaap:StateAndLocalJurisdiction


Operating
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value27481777777249.4712.919
Percentage of OperatingLossCarryforwards5679.11681.21309.41309.41309.1413.9160.349.4

us-gaap:PrepaidExpenseCurrent

us-gaap:PrepaidExpenseCurrent


Prepaid
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value9802000.09933000.08158000.08892000.05043000.05884000.05672000.06230000.05893000.01333000.01261000.01727000.01551000.02693000.03085000.03511000.03347000.01575000.01879000.01534000.0928000.01530000.02287000.02310000.01203000.01544000.01827000.0859000.0460000.01089000.0667000.0501000.0429000.0779000.0
Percentage of PrepaidExpenseCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RestrictedCash

us-gaap:RestrictedCash


Restricted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-30
Value620000.0620000.0620000.0620000.0321000.0320000.0000
Percentage of RestrictedCash100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:RestrictedCashNoncurrent

us-gaap:RestrictedCashNoncurrent


Restricted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312018-12-312017-12-31
Value600000.0600000.0620000.0600000.0600000.0300000.0321000.000
Percentage of RestrictedCashNoncurrent100.0100.0100.0100.0100.0100.0100.00.00.0

us-gaap:SaleOfStockPricePerShare us-gaap:CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProject, us-gaap:SubsequentEventType

us-gaap:SaleOfStockPricePerShare

mrtx:LicenseAgreementwithORICPharmaceuticalsInc., us-gaap:SubsequentEvent


Sale
Period End2020-08-03
Value34.0
Percentage of SaleOfStockPricePerShare100.0

us-gaap:SecurityDeposit

us-gaap:SecurityDeposit


Security
Period End2020-12-312013-09-302013-06-302012-12-31
Value600000.099000.0101000.067000.0
Percentage of SecurityDeposit100.0100.0100.0100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

us-gaap:RestrictedStockUnitsRSU


Share
Period End2020-12-31
Value114.14
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant us-gaap:PlanName

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant

mrtx:A2013EquityIncentivePlan


Share
Period End2020-12-312019-12-31
Value1500000.02200000.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant100.0100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice


Share
Period End2020-12-31
Value33.62
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue


Share
Period End2020-12-31
Value712
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue100.0

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding us-gaap:AwardType

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding

us-gaap:RestrictedStockUnitsRSU


Sharebased
Period End2020-12-31
Value102
Percentage of SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding100.0

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1


Sharebased
Period End2020-12-31
Value441
Percentage of SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1100.0

us-gaap:TaxCreditCarryforwardAmount us-gaap:IncomeTaxAuthority, us-gaap:TaxCreditCarryforward

us-gaap:TaxCreditCarryforwardAmount

us-gaap:InternalRevenueServiceIRS, us-gaap:Research


Tax
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312013-12-31
Value2917107.24.42.20.2
Percentage of TaxCreditCarryforwardAmount100.0100.0100.0100.0100.0100.0100.0

us-gaap:StateAndLocalJurisdiction, us-gaap:Research


Tax
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312013-12-31
Value117.24.72.92.01.40.1
Percentage of TaxCreditCarryforwardAmount38.041.944.340.345.563.650.0

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