BIIB


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

Table of contents



us-gaap:CommonStockValue
us-gaap:StatementEquityComponents
us-gaap:SharesIssued

us-gaap:CommonStockSharesIssued

us-gaap:CommonStockSharesOutstanding
us-gaap:StatementEquityComponents

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:AllocatedShareBasedCompensationExpense
us-gaap:AwardType
us-gaap:IncomeStatementLocation
us-gaap:StatementEquityComponents

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:CostOfGoodsAndServicesSold

us-gaap:CostOfRevenue

us-gaap:CostsAndExpenses

us-gaap:GrossProfit

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments

us-gaap:IncomeTaxExpenseBenefit
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:InterestExpense

us-gaap:NetIncomeLoss
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NonoperatingIncomeExpense
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:OperatingExpenses

us-gaap:OperatingIncomeLoss

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:RealizedInvestmentGainsLosses
us-gaap:TypeOfArrangement
us-gaap:ResearchAndDevelopmentExpense

us-gaap:ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost
us-gaap:TypeOfArrangement

us-gaap:Revenues
us-gaap:MajorCustomers, us-gaap:ProductOrService
us-gaap:MajorCustomers, us-gaap:TypeOfArrangement
us-gaap:ProductOrService
us-gaap:ProductOrService, us-gaap:StatementGeographical
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:TypeOfArrangement

us-gaap:SellingGeneralAndAdministrativeExpense

us-gaap:Assets

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity

us-gaap:AssetsCurrent

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:AccountsReceivableNetCurrent

us-gaap:InventoryNet

us-gaap:OtherAssetsCurrent

us-gaap:Land

us-gaap:MachineryAndEquipmentGross

us-gaap:NoncurrentAssets
us-gaap:StatementGeographical

us-gaap:PropertyPlantAndEquipmentGross
biib:FacilityLocation

us-gaap:FurnitureAndFixturesGross

us-gaap:LeaseholdImprovementsGross

us-gaap:ConstructionInProgressGross
biib:FacilityLocation

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:AmortizationOfIntangibleAssets

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:Goodwill
biib:Researchanddevelopmentasset, us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass
us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill
us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass

us-gaap:IntangibleAssetsNetExcludingGoodwill
biib:Researchanddevelopmentasset, us-gaap:FairValueByMeasurementFrequency
biib:Researchanddevelopmentasset, us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:DeferredTaxAssetsLiabilitiesNet

us-gaap:OperatingLeaseRightOfUseAsset
us-gaap:BalanceSheetLocation

us-gaap:OtherAssetsNoncurrent

us-gaap:EquitySecuritiesFvNi
us-gaap:FinancialInstrument

us-gaap:AccountsPayableCurrent

us-gaap:LiabilitiesCurrent
us-gaap:BalanceSheetLocation
us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:OtherAccruedLiabilitiesCurrent
us-gaap:BalanceSheetLocation

us-gaap:OtherLiabilitiesCurrent
us-gaap:BalanceSheetLocation

us-gaap:TaxesPayableCurrent

us-gaap:LongTermDebt
us-gaap:LongtermDebtType

us-gaap:DeferredIncomeTaxLiabilitiesNet

us-gaap:MinorityInterest

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent
us-gaap:BalanceSheetLocation

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

us-gaap:OperatingLeaseLiability

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:StockholdersEquity

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
us-gaap:StatementEquityComponents

us-gaap:CommonStockValue

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:TreasuryStockValue

us-gaap:MinorityInterest

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:DepreciationDepletionAndAmortization

us-gaap:IncreaseDecreaseInAccountsReceivable

us-gaap:IncreaseDecreaseInInventories

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:ShareBasedCompensation

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:ProceedsFromIssuanceOfLongTermDebt

us-gaap:PaymentsForRepurchaseOfCommonStock
us-gaap:ShareRepurchaseProgram

us-gaap:EffectiveIncomeTaxRateContinuingOperations

us-gaap:DeferredTaxLiabilities

us-gaap:DeferredTaxAssetsNet

us-gaap:UnrecognizedTaxBenefits

us-gaap:DeferredTaxAssetsValuationAllowance

biib:AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears
us-gaap:ValuationAllowancesAndReservesType

biib:AmortizationAndImpairmentOfAcquiredIntangibleAssets
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
biib:Biogenshareofcopromotionprofitsorlosses

biib:Collaborationprofitlosssharing
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

biib:CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear
us-gaap:ValuationAllowancesAndReservesType
us-gaap:DebtInstrument
biib:DebtInstrumentRedemptionAmount
us-gaap:ProductOrService
biib:DeferredTaxAssetIncreaseDecreaseInValue
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
biib:Derivativesusedinnetinvestmenthedgenetoftaxexcludedcomponentincreasedecrease
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
biib:EarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCosts

biib:EffectiveTaxRateReconciliationGILTItax

biib:EffectiveTaxRateReconciliationNuerImmuneTaxImpacts
us-gaap:ProductOrService, us-gaap:TypeOfArrangement
biib:ExpenseIncurredByCollaboration
us-gaap:TypeOfArrangement
us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement
biib:Expenseincurredbythecollaboration
us-gaap:ProductOrService, us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement
us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement
biib:Expensereflectedwithinstatementsofincome
us-gaap:ProductOrService, us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement
us-gaap:ProductOrService, us-gaap:TypeOfArrangement
us-gaap:TypeOfArrangement
us-gaap:TypeOfArrangement
biib:GlobalLicensingCollaborationAgreementAmountSharesPurchased
us-gaap:TypeOfArrangement
biib:GlobalLicensingCollaborationAgreementPurchasePricePerShare
us-gaap:TypeOfArrangement
biib:GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryAndCommercialMilestonePayments
us-gaap:TypeOfArrangement
biib:GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryandCommercialMilestonePayments
us-gaap:TypeOfArrangement
biib:GlobalLicensingCollaborationAgreementSharesPurchased
us-gaap:TypeOfArrangement
biib:GlobalLicensingCollaborationAgreementSharesPurchasedPerShare

biib:IncomeLossFromEquityMethodInvestmentsNetOfTax
us-gaap:ProductOrService
biib:IncomeTaxExpenseReductioninDeferredTaxAssetsandLiabilitiesNet
us-gaap:DebtInstrument
biib:LongTermDebtExchangedAmount

biib:NoncontrollingInterestCapitalContribution
us-gaap:StatementEquityComponents

biib:NoncontrollingInterestIncreaseDecreaseOther
us-gaap:StatementEquityComponents

biib:Noncontrollinginterestincreasedecreaseother
us-gaap:StatementEquityComponents
us-gaap:MajorCustomers
biib:OtherrevenuesfromantiCD20therapeuticprograms

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToCurrentYear
us-gaap:ValuationAllowancesAndReservesType

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear
us-gaap:ValuationAllowancesAndReservesType
us-gaap:DebtInstrument, us-gaap:IncomeStatementLocation, us-gaap:LongtermDebtType
biib:PretaxChargePaymentofEarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCostsNetofDerivativeGain
us-gaap:ConsolidatedEntities
biib:ResearchAndDevelopmentCostsPercentage

biib:ShareBasedCompensationExpenseIncludedInCostsAndExpenses
us-gaap:MajorCustomers
biib:ShareOfCoPromotionProfits

biib:TechnologicalAndRegulatorySuccessProbability

us-gaap:AllocatedShareBasedCompensationExpenseNetOfTax

us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationAsset1

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect

us-gaap:DebtSecuritiesAvailableForSaleRealizedGain

us-gaap:DebtSecuritiesAvailableForSaleRealizedLoss

us-gaap:Depreciation
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation
us-gaap:DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation
us-gaap:DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DiscontinuedOperationTaxEffectOfDiscontinuedOperation

us-gaap:EffectOfExchangeRateOnCashAndCashEquivalents

us-gaap:EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciationAndAmortization

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseImpairmentLosses

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther

us-gaap:EffectiveIncomeTaxRateReconciliationOtherAdjustments

us-gaap:EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes

us-gaap:EffectiveIncomeTaxRateReconciliationTaxCredits

us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount

us-gaap:EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense

us-gaap:EquitySecuritiesFvNiGainLoss

us-gaap:EquitySecuritiesFvNiRealizedGainLoss

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss
dei:LegalEntity
dei:LegalEntity
us-gaap:EquitySecuritiesFvNiUnrealizedLoss

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation
us-gaap:GainLossOnDerivativeInstrumentsNetPretax
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

us-gaap:GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments

us-gaap:GoodwillOtherIncreaseDecrease
biib:Researchanddevelopmentasset, us-gaap:BusinessAcquisition
us-gaap:ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill
biib:Researchanddevelopmentasset, us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:IncomeLossFromEquityMethodInvestments
us-gaap:ProductOrService, us-gaap:TypeOfArrangement
us-gaap:TypeOfArrangement
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions

us-gaap:IncreaseDecreaseInAccruedIncomeTaxesPayable

us-gaap:IncreaseDecreaseInAccruedLiabilities

us-gaap:IncreaseDecreaseInDueFromRelatedParties

us-gaap:IncreaseDecreaseInEquitySecuritiesFvNi
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities
us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InvestmentIncomeInterest

us-gaap:OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
us-gaap:StatementEquityComponents
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation
us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation
us-gaap:OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseBeforeAdjustmentsAndTax

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherNoncashIncomeExpense

us-gaap:PaymentsForProceedsFromOtherInvestingActivities

us-gaap:PaymentsOfFinancingCosts

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt

us-gaap:PaymentsToAcquireInProcessResearchAndDevelopment

us-gaap:PaymentsToAcquireIntangibleAssets
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:PaymentsToAcquireInterestInSubsidiariesAndAffiliates

us-gaap:PaymentsToMinorityShareholders

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesEquity

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
us-gaap:StatementEquityComponents

us-gaap:RepaymentsOfDebt

us-gaap:RepaymentsOfSeniorDebt
us-gaap:DebtInstrument

us-gaap:ResearchAndDevelopmentInProcess
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesTreasuryStockReissued

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueTreasuryStockReissued
us-gaap:StatementEquityComponents
us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents
us-gaap:StockRepurchasedAndRetiredDuringPeriodShares

us-gaap:StockholdersEquityOther
us-gaap:StatementEquityComponents

us-gaap:TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense

us-gaap:TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents
us-gaap:TreasuryStockRetiredCostMethodAmount
us-gaap:ShareRepurchaseProgram
us-gaap:TreasuryStockSharesAcquired
us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
us-gaap:ShareRepurchaseProgram
us-gaap:TreasuryStockValueAcquiredCostMethod
us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:UnrealizedGainLossOnForeignCurrencyDerivativesNetBeforeTax

us-gaap:UnrealizedGainLossOnInvestments

us-gaap:WeightedAverageNumberDilutedSharesOutstandingAdjustment

biib:AccruedExpensesOnFundingCommitmentRelatedToClinicalResearch
us-gaap:ProductOrService, us-gaap:TypeOfArrangement
biib:AdditionalMilestonePayment
us-gaap:TypeOfArrangement

biib:AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsAmortizedCost

biib:AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsFairValue

biib:Collaborationexpensesaccrual
us-gaap:BalanceSheetLocation

biib:ComputerSoftwareAndHardware
us-gaap:ProductOrService
biib:DeferredTaxAssetsValueReductionInValue
us-gaap:ProductOrService
biib:DeferredTaxAssetsValueReductioninValue

biib:DeferredTaxLiabilitiesDepreciationAmortizationOther

biib:DeferredTaxLiabilitiesTaxCreditCarryforwards
us-gaap:ProductOrService
biib:DeferredTaxLiabilitiesValueReductionInValue
us-gaap:ProductOrService
biib:DeferredTaxLiabilitiesValueReductioninValue

biib:DeferredtaxliabilitiesGILTItaxcalculation

biib:Deferredtaxliabilitiestemporarydifferencespurchaseaccountingforeignsubsidiaries

biib:DueFromUnconsolidatedJointBusiness

biib:DuefromantiCD20therapeuticprograms

biib:EquitySecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:FinancialInstrument

biib:EquitySecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:FinancialInstrument
us-gaap:TypeOfArrangement
biib:EstimatedAdditionalPaymentsUponAchievementOfDevelopmentAndCommercialMilestones
us-gaap:BusinessAcquisition, us-gaap:MeasurementInputType
biib:FairValueMeasurementInputs

biib:Inventorynetcurrentandnoncurrent

biib:InvestmentInBiotechnologyCompaniesThatAreDeterminedToBeUnconsolidatedVariableInterestEntities
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel
biib:InvestmentInCommonStockSharesPurchased
dei:LegalEntity
biib:Investmentincommonstocksharespurchased
us-gaap:ProductOrService
biib:PercentageOfCoPromotionOperatingProfitsFirstFiftyMillion
us-gaap:ProductOrService
biib:PercentageOfCoPromotionOperatingProfitsGreaterThanFirstFiftyMillionOptionOne
us-gaap:ProductOrService
biib:PercentageOfCoPromotionOperatingProfitsGreaterThanFirstFiftyMillionOptionTwoSubOptionOne
us-gaap:ProductOrService
biib:PercentageOfCoPromotionOperatingProfitsGreaterThanFirstFiftyMillionOptionTwoSubOptionThree
us-gaap:ProductOrService
biib:PercentageOfCoPromotionOperatingProfitsGreaterThanFirstFiftyMillionOptionTwoSubOptionTwo
biib:MajorDistributor
biib:PercentageReceivablesOfWholesaleDistributorAccountedInConsolidatedReceivables
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
biib:PlanAssetsForDeferredCompensationFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency

biib:PotentialFutureMilestonePaymentsCommitmentToThirdPartyApproximately
biib:ExpectedPaymentTimelineofMilestone
biib:FutureContingentMilestoneTypes
biib:FutureContingentMilestoneTypes, us-gaap:ConsolidatedEntities
biib:FutureContingentMilestoneTypes, us-gaap:ConsolidatedEntities, us-gaap:ProductOrService, us-gaap:TypeOfArrangement
biib:FutureContingentMilestoneTypes, us-gaap:ProductOrService, us-gaap:StatementGeographical, us-gaap:TypeOfArrangement
biib:FutureContingentMilestoneTypes, us-gaap:StatementGeographical, us-gaap:TypeOfArrangement
us-gaap:StatementScenario, us-gaap:SubsequentEventType, us-gaap:TypeOfArrangement
us-gaap:StatementScenario, us-gaap:TypeOfArrangement
us-gaap:BalanceSheetLocation, us-gaap:FinancialInstrument
biib:StrategicInvestmentPortfolio
us-gaap:FinancialInstrument

biib:Totaldeferredchargesandprepaidtaxes

biib:UnrealizedGainLossesOnForeignCurrencyDerivativesNetBeforeTax
biib:DerivativeMaturity

biib:UnrealizedGrossGainsOnForeignCurrencyDerivativesNetBeforeTax

biib:UnrealizedGrossLossesOnForeignCurrencyDerivativesNetBeforeTax
us-gaap:TypeOfArrangement
biib:UpfrontAndMilestonePaymentsMadeToCollaborativePartner

dei:EntityCommonStockSharesOutstanding

us-gaap:AccruedIncomeTaxesNoncurrent

us-gaap:AccruedRoyaltiesCurrent
us-gaap:BalanceSheetLocation
us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:AociDerivativeQualifyingAsHedgeExcludedComponentAfterTax
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:AssetsFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleSecurities
us-gaap:FinancialInstrument
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleSecuritiesAmortizedCost

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue

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

us-gaap:AvailableForSaleSecuritiesDebtSecuritiesCurrent

us-gaap:AvailableForSaleSecuritiesDebtSecuritiesNoncurrent

us-gaap:BuildingsAndImprovementsGross

us-gaap:BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationContingentConsiderationLiability
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency

us-gaap:BusinessCombinationContingentConsiderationLiabilityCurrent
us-gaap:BalanceSheetLocation
us-gaap:MeasurementInputType
us-gaap:BusinessCombinationContingentConsiderationLiabilityMeasurementInput
us-gaap:Range, us-gaap:MeasurementInputType

us-gaap:BusinessCombinationContingentConsiderationLiabilityNoncurrent
us-gaap:ContingentConsiderationByType
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:CashAndCashEquivalentsFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency

us-gaap:CashEquivalentsAtCarryingValue
us-gaap:InvestmentType

us-gaap:ConstructionPayableCurrentAndNoncurrent
biib:FacilityLocation
biib:FacilityLocation
us-gaap:ContractualObligation

us-gaap:DebtInstrumentFairValue

us-gaap:DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible
us-gaap:RetirementPlanType
us-gaap:DeferredCompensationLiabilityClassifiedNoncurrent

us-gaap:DeferredIncomeTaxAssetsNet

us-gaap:DeferredTaxAssetsGoodwillAndIntangibleAssets

us-gaap:DeferredTaxAssetsGross

us-gaap:DeferredTaxAssetsInventory

us-gaap:DeferredTaxAssetsOperatingLossCarryforwards
us-gaap:IncomeTaxAuthority, us-gaap:TaxCreditCarryforward
us-gaap:DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration

us-gaap:DeferredTaxAssetsOther

us-gaap:DeferredTaxAssetsTaxCreditCarryforwards

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost

us-gaap:DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets
us-gaap:IncomeTaxAuthority
us-gaap:DeferredTaxLiabilitiesUndistributedForeignEarnings
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanBenefitObligation
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanFundedStatusOfPlan
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:DerivativeFairValueOfDerivativeAsset
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:BalanceSheetLocation, us-gaap:HedgingDesignation
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:DerivativeFairValueOfDerivativeLiability
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:BalanceSheetLocation, us-gaap:HedgingDesignation
us-gaap:BalanceSheetLocation
us-gaap:DerivativeLiabilitiesCurrent
us-gaap:Currency, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeNotionalAmount
us-gaap:Currency, us-gaap:HedgingDesignation
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:HedgingDesignation
us-gaap:TypeOfArrangement
us-gaap:DueFromRelatedParties
us-gaap:TypeOfArrangement
us-gaap:DueToRelatedPartiesCurrentAndNoncurrent

us-gaap:EmployeeRelatedLiabilitiesCurrent
us-gaap:BalanceSheetLocation

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquityMethodInvestmentOwnershipPercentage
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquityMethodInvestments

us-gaap:EquitySecuritiesFvNiCost
us-gaap:FinancialInstrument

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFive

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFour

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearThree

us-gaap:FiniteLivedIntangibleAssetsGross
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:ForeignCurrencyContractAssetFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:ForeignCurrencyContractsLiabilityFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency
biib:Researchanddevelopmentasset, us-gaap:FairValueByMeasurementFrequency
us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwillFairValueDisclosure

us-gaap:IntangibleAssetsGrossExcludingGoodwill

us-gaap:InventoryFinishedGoodsNetOfReserves

us-gaap:InventoryRawMaterialsNetOfReserves

us-gaap:InventoryWorkInProcessNetOfReserves
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:InvestmentsFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:LiabilitiesFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency

us-gaap:LiabilityForUncertainTaxPositionsCurrent

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo

us-gaap:LongTermNotesPayable
us-gaap:DebtInstrument, us-gaap:LongtermDebtType

us-gaap:LossContingencyEstimateOfPossibleLoss

us-gaap:NotesPayable
us-gaap:DebtInstrument

us-gaap:NotesPayableFairValueDisclosure
us-gaap:DebtInstrument

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent
us-gaap:IncomeTaxAuthority, us-gaap:TaxCreditCarryforward
us-gaap:OperatingLossCarryforwards

us-gaap:OtherCommitment
biib:FacilityLocation
us-gaap:TypeOfArrangement
us-gaap:OtherInventoryCapitalizedCosts
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:PurchaseCommitmentRemainingMinimumAmountCommitted
us-gaap:ProductOrService
us-gaap:RevenueRemainingPerformanceObligation
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
us-gaap:ShareRepurchaseProgram
us-gaap:StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
us-gaap:IncomeTaxAuthority, us-gaap:TaxCreditCarryforward
us-gaap:TaxCreditCarryforwardAmount

us-gaap:TreasuryStockShares

us-gaap:UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued

us-gaap:UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate

us-gaap:ValuationAllowancesAndReservesBalance
us-gaap:BalanceSheetLocation
us-gaap:ValuationAllowancesAndReservesType

Plots across concepts


IncomeStatement
Other Comprehensive Income Loss Net Of Tax
Expenses
Income Tax Expense Benefit
Balance Sheet
Operating Lease Right Of Use Asset
Assets
Operating Lease Right Of Use Asset
Current Assets
Other Assets Current
NonCurrent Assets
Operating Lease Right Of Use Asset
PropertyPlantAndEquipmentNet
Accumulated Depreciation Depletion And Amortization Property Plant And Equipment
Liabilities
Operating Lease Liability
Current Liabilities
Taxes Payable Current
Noncurrent Liabilities
Operating Lease Liability Noncurrent
Stockholders Equity
Accumulated Other Comprehensive Income Loss Net Of Tax
CashFlow
Net Cash Provided By Used In Financing Activities
NetCashProvidedByUsedInOperatingActivities
Increase Decrease In Accounts Receivable
NetCashProvidedByUsedInInvestingActivities
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInFinancingActivities
Net Cash Provided By Used In Financing Activities
Shares
Treasury Stock Shares
OperatingLeaseLiability
Operating Lease Liability Noncurrent
NonoperatingIncomeExpense
Other Nonoperating Income Expense
LesseeOperatingLeaseLiabilityPaymentsDue
Lessee Operating Lease Liability Undiscounted Excess Amount
FiniteLivedIntangibleAssets
Finite Lived Intangible Assets Net
InventoryNet
Inventory Finished Goods Net Of Reserves

Tables

  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:CommonStockValue ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▇█████████████████▇▇0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.1240.1290.1290.1290.1290.1280.1280.1280.1280.1280.1280.1270.1270.1270.1290.1280.1280.1270.1250.124NANANA0.144NANANA
 us-gaap:SharesIssued us-gaap:StatementEquityComponents us-gaap:CommonStockNANA176.2NANA191.1198.0205.7208.6219.0221.0225.2201.4234.8235.3NANANA238.5NANANA241.2NANANA257.126NANANA255.973NANANA254.237NANANA0.255633NANANA248.2NANANA288.494NANANA
 us-gaap:SharesIssued us-gaap:StatementEquityComponents us-gaap:TreasuryStockNANA23.8NANA23.823.823.823.823.823.823.823.823.823.8NANANA22.6NANANA22.6NANANA22.562NANANA-19.641NANANA-17.655NANANA-0.013518NANANA-7.662NANANA-13.639NANANA
us-gaap:CommonStockSharesIssued NANA176.2NANANA198.0NANANA221.0NANANA235.3NANANA238.5NANANA241.2NANANA257.126NANANA255.973NANANA254.237NANANA255.633NANANA0.2482NANANA0.288494NANANA
us-gaap:CommonStockSharesOutstanding NANA152.4NANANA174.2NANANA197.2NANANA211.5NANANA215.9NANANA218.6NANANA234.563NANANA236.332NANANA236.582NANANA242.115NANANA0.240538NANANA0.274855NANANA
 us-gaap:CommonStockSharesOutstanding us-gaap:StatementEquityComponents us-gaap:CommonStock▁▁▁▂▂▄▅▆▆██172.9174.4176.2177.7182.1191.1198.0205.7208.6219.0221.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding ▁▁▁▂▂▃▃▄▄▅▅▅▆▆▆▆▆▆▆▇▇▇▇███████150.1152.3154.0157.2160.9173.1178.2184.2190.4197.0200.3201.9207.3211.7212.0211.8212.2215.9217.0219.4219.4219.3220.8232.612235.718235.63236.3236.972237.401237.849NA238.349238.743238.304NA238.125240.622241.828NA245.366244.966244.551NA242.313261.658272.703NANANANA
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic ▁▁▁▂▂▃▃▄▄▅▅▅▆▆▆▆▆▆▆▇▇▇▇███████149.7151.9153.7156.9160.6172.8177.8184.0190.3196.6199.8201.4207.1211.4211.5211.4211.9215.6216.6218.9219.1218.9220.4232.191235.286234.995235.5236.217236.661236.786NA237.07237.484236.837NA236.474238.988239.754NA242.883242.375241.536NA239.864259.938269.922NANANANA
us-gaap:EarningsPerShareBasic ▄▄▃▅█▇▇▇▇▆▅▆▅▅▁▆▄▄▄▅▅▅▄▅▄▄▄▄▄▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▃▃▂▂3.02.72.334.479.68.18.18.47.857.174.747.174.185.55-1.415.84.073.473.04.724.794.443.774.163.943.53.753.633.022.031.942.062.071.81.241.681.621.261.241.451.191.221.01.061.130.81.070.960.490.85
us-gaap:EarningsPerShareDiluted ▄▄▃▅█▇▇▇▇▆▅▆▅▅▁▆▄▄▄▅▅▅▄▅▄▄▄▄▄▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▃▂▂▂2.992.692.324.469.598.088.088.397.857.154.737.154.185.54-1.45.794.073.462.994.714.794.433.774.153.933.493.743.623.012.021.922.052.061.791.231.671.611.251.221.431.181.20.991.051.120.81.060.950.490.84
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
 TTM Greenblatt ROC _ _▃▅▁▅██▇▇█▇▆▇▆▇▆▇▆▅▅▆▆▆▆▆▆▅▆▆▅▄▄▄▄▄▃▄▄▃▃▃▃▃▃485.7973.9-330.61086.41974.51819.91777.71806.31955.91502.71443.11697.61213.21534.71465.81653.51200.61024.3886.21425.31460.51378.41168.1971371.8321233.0961117.8751159.7631152.578988.725671.348657.926684.531662.527510.525445.507535.25505.723369.37409.103488.493410.813416.283355.186NANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:AllocatedShareBasedCompensationExpense ▂▁▂▃▂▁▇███▇▇▇█-55.8-72.6-50.3-35.4-49.5-69.239.447.855.049.040.740.441.446.7NANANANANANANANANANANANANANANANANANANANANANANANA6.34736.636.1NA26.33542.849.4NANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType biib:CashSettledPerformanceSharesNANANA0.0-0.1-1.6NA0.30.4-1.0NA5.8-0.74.3NA7.02.53.5NA7.94.60.2NA-9.53.2NANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType biib:EmployeeStockPurchasePlan▁█3.36.9NA3.15.62.3NA1.73.44.6NA1.92.13.9NA1.72.13.6NA2.72.53.7NA2.93.0NANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType biib:MarketStockUnits▁█9.316.5NA5.57.419.1NA9.37.87.7NA7.47.16.1NA4.53.09.6NA5.77.913.4NA7.39.1NANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType biib:PerformanceStockUnitsSettledinCash▁█3.46.0NA4.1-4.08.9NA1.30.91.0NA1.10.30.1NA0.00.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType biib:PerformanceStockUnitsSettledinStock▁█3.06.3NA-8.42.110.3NA-1.112.12.0NA1.31.40.7NA0.00.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType biib:TimeVestedRestrictedStockUnits▁█40.442.8NA35.334.537.5NA37.931.834.7NA29.930.636.1NA26.727.626.9NA28.533.930.1NA30.431.8NANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType us-gaap:PerformanceSharesNANANA0.00.0-0.1NA0.20.30.5NA3.02.0-0.8NA3.21.24.5NA9.11.36.9NA-2.81.2NANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:IncomeStatementLocation us-gaap:Parent▅▇▄▃▄▇▃▄█▄▃▄▃▄▂▃▂▃▃▄▃▃▂▁▃▇▄▄▄▆▅▄▅▄▃▃▂46.861.940.732.337.061.635.739.866.538.830.539.233.539.429.129.725.533.030.636.133.136.027.319.133.260.939.540.039.051.745.440.846.140.632.331.229.1NANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:IncomeStatementLocation us-gaap:ResearchAndDevelopmentExpense▃▇▃▂▂▇▁▂▆▄▂▄▃▄▃▃▃▃▃▄▄▄▄▁▄█▅▅▅▆▅▄▅▅▃▃▃19.133.616.914.615.233.311.915.428.121.715.321.017.621.918.319.517.518.718.922.721.521.420.310.822.135.424.024.224.529.426.020.723.725.218.918.018.1NANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:IncomeStatementLocation us-gaap:SellingGeneralAndAdministrativeExpenses▅▆▄▂▃▆▄▄█▃▂▃▂▃▂▂▁▃▃▄▃▄▃▁▃█▄▄▄▆▅▅▆40.344.932.9000000000000125.030.343.131.534.254.827.822.729.425.228.523.823.618.929.427.131.228.734.728.017.526.255.634.834.733.647.240.839.945.4NANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital▂▁▂▃▂▁▇███▇▇▇█-55.8-72.6-50.3-35.4-49.5-69.239.447.855.049.040.940.241.446.7NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AllocatedShareBasedCompensationExpense us-gaap:StatementEquityComponents us-gaap:Parent▂▁▂▃▂▁▃▂▂█-55.8-72.6-50.3-35.4-49.5-69.2-39.4-47.8-55.049.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:ComprehensiveIncomeNetOfTax ▄▄▃▄▇▇▇█▇▇▅▇▅▆▁▆▅▅▄▆▆▅▅▅▅▅▅▅▅▄▄▄▄▃▃▃▃▃▃▃▃▃451.0534.9284.4657.01510.41385.01396.81706.51461.01429.4954.71457.7908.91185.9-286.41235.5849.2742.3630.21014.81026.3935.6764.989909.231896.789811.491861.963845.549710.184485.345458.876513.436503.509414.079287.873397.84354.294311.257228.965334.714333.672332.147NANANANANANANANA
us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest █▂▂▂▂▂▂▂▂▂▃▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂576.9-4.9-0.21.5-65.5-5.9-0.80.00.40.088.11.5-48.41.7-131.10.00.00.11.42.61.41.72.853-53.5862.2662.2670.8790.738-8.6260.2280.00.00.00.0-0.130.00.295-0.23-74.3281.0318.93317.199NANANANANANANANA
us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest ▅▄▃▄█▇▇█▇▇▅▇▅▆▁▆▅▄▄▅▅▅▄▅▅▅▅▅▄▃▃▄▃▃▃▃▃▃▃▃▃▃▃▂▂▂1027.9530.0284.2658.51575.91379.11396.81706.51460.61429.4952.41456.2957.31184.2-155.31235.5849.2742.2628.81012.21024.9933.9762.136962.817894.523809.224861.084844.811718.81485.117458.876513.436503.509414.079288.003397.84353.999311.487266.164334.7333.6332.1258.427136.0239.2189.9NANANANA
us-gaap:CostOfGoodsAndServicesSold ▄▄▅▃▂▄▃▃▄█▅▄▃▃▅▁▁459.7478.1490.6449.1411.1454.3447.1430.0476.3602.0488.5460.8421.0446.0509.2370.0366.2NANANANANANANANANANANANANANANANA133.749133.828139.358139.112133.197139.637123.527100.503103.113100.30495.918106.98597.055NANANANA
us-gaap:CostOfRevenue ▄▄▅▃▂▄▃▃▄█▅▄▃▃▅▁▁459.7478.1490.6449.1411.1454.3447.1430.0476.3602.0488.5460.8421.0446.0509.2370.0366.2NANANANANANANANANANANANANANANANA133.749133.828139.358139.112133.197139.637123.527100.503103.113100.30495.918106.98597.055NANANANA
us-gaap:CostsAndExpenses ▅▄█▅▄▄▄▄▄▅▅▄▅▃▄▃▄▄▅▃▃▃▄▃▃▃▃▃▃▃▃▂▂▁▂▁▁▁▁▁▁▁▁▂▁▁2289.31720.13183.22289.71707.11714.41893.61793.81660.81987.12083.21741.42143.31596.41841.21424.31877.81786.41985.81530.51433.71348.41671.1391406.0271358.5461437.0881485.5321363.2471436.6271462.2621315.5031150.1981066.265909.622987.507882.023915.228922.644917.607821.441797.834787.059863.886981.654816.822805.171NANANANA
us-gaap:GrossProfit NANA2361.92927.03270.53080.03224.23170.13140.42887.83037.82978.22935.52685.12797.82707.82712.22426.12493.52538.92523.92413.82507.52467.92305.52242.62343.42208.82129.61850.51707.31593.11492.81281.41284.11246.21281.81158.81187.11186.41108.11100.21118.81079.91105.71011.81027.31027.01002.6938.3
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments ▂▂▂▄█▇▇▇▇▇▆▇▅▆▆▆▅▄▃▅▆▅▄▅▅▄▅▅▄▃▃▃▃▂▂▂▂▂▂▂▂▂▂▁▂▁582.1467.0352.9957.82037.51699.41728.41779.01758.51860.01414.51812.71178.71493.71399.81609.91132.4986.7838.21367.21402.01325.61085.7851356.4191222.2071102.8891151.0121136.288993.586665.747652.521679.891652.099496.068431.217530.702508.673384.514405.13480.766399.085426.234350.521187.19396.892295.303NANANANA
us-gaap:IncomeTaxExpenseBenefit ▁▃▂▃▄▃▃▃▃▄▄▄▃▄█▄▃▃▃▄▄▄▃▄▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃-409.144.213.3240.8446.1292.0276.1211.3248.1422.5469.6369.8263.7322.51566.1383.8269.6239.2190.3337.0353.6356.4257.125330.093292.501281.881268.233274.774268.521178.414190.261186.105159.1465.508136.341131.044121.02182.148104.92127.10495.036117.46878.76975.011102.24375.31NANANANA
 us-gaap:IncomeTaxExpenseBenefit us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome,us-gaap:StatementEquityComponents us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome,us-gaap:AccumulatedGainLossNetCashFlowHedgeParent█▇▂▂▁▁▁▁▁▁▂▂▂▂▂▂▂3.02.30.00.1-0.1-0.1-0.3-0.1-0.1-0.10.00.00.10.10.10.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:IncomeTaxExpenseBenefit us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome,us-gaap:StatementEquityComponents us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome,us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss▄▄▃▄▃▆▃▄▄▄▄▄▄▅█▄▄▄▄▄▄▄▄▄▄▄▄▄▁▄▁▄▄▃▃▄▄0.10.1-0.90.0-0.83.4-0.6-0.1-0.1-0.10.20.00.01.66.20.30.00.30.10.00.20.00.10.50.10.00.10.0-3.60.0-3.9-0.10.0-1.4-0.90.10.3NANANANANANANANANANANANANA
 us-gaap:IncomeTaxExpenseBenefit us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName biib:SamsungBiosimilarAgreement31.2NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:InterestExpense ▇█▇▇█▅▆▆▆▆▆▆▆▆▇▇███████▂▁▁▁▁▁▁▁▁▁▂▂▁▁▁▁▁▁▁▁▁▁▁56.464.756.056.366.044.346.045.847.747.949.449.051.750.562.061.863.663.464.866.065.963.367.415.65.86.77.47.47.17.66.46.67.311.513.48.77.07.47.57.98.49.29.59.39.08.3NANANANA
us-gaap:NetIncomeLoss ▄▄▃▅█▇███▇▆█▅▇▁▇▅▅▅▆▆▆▅▆▆▅▅▅▅▄▄▄▄▄▃▄▄▃▃▃▃▃▃▃▃▃▃▃▃▃448.5410.2357.9701.51542.11399.11439.71545.91494.11408.8946.81444.4866.61172.9-297.41226.1862.8747.6649.21032.91049.8970.9831.6965.622927.276822.541883.5856.858714.506479.956457.3487.616490.67426.749292.1398.4386.846302.661300.2351.826288.034294.331240.3254.1293.4217.4305.6277.7142.8244.0
us-gaap:NetIncomeLossAttributableToNoncontrollingInterest █▂▂▂▃▂▂▂▂▂▂▂▃▂▄▂▂▂▂▂▂▂▂▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▁▂▂▂▂▂▂577.0-5.6-0.32.464.4-6.50.00.00.00.0-1.9-1.548.4-1.7131.10.00.0-0.1-1.3-2.7-1.4-1.7-2.85353.871-2.451-2.367-0.879-0.7388.626-0.2280.00.00.00.00.00.00.295-0.295-0.0281.83616.01514.43531.5-141.91.22.60.41.92.02.6
us-gaap:NonoperatingIncomeExpense ▅▁█▃▄▃▄▄▃▆▄▅▄▄▄▄▄▄▄▄▄▄▃▄▄▄96.4-506.9683.5-128.663.0-120.5-49.3-27.3-197.4357.3-28.6115.1-34.5-41.0-66.0-43.6-68.2-37.6-48.0-58.1-58.5-52.8-82.412-15.413-10.889-15.0NA-16.294.861NANANANANANANANANANANANANANANANANANANANANA
us-gaap:OperatingIncomeLoss ▃▅▁▅██▇▇█▇▆▇▆▇▆▇▆▅▅▆▆▆▆▆▆▅▆▆▅▄▄▄▄▄▃▄▄▃▃▃▃▃▃▃▃▃485.7973.9-330.61086.41974.51819.91777.71806.31955.91502.71443.11697.61213.21534.71465.81653.51200.61024.3886.21425.31460.51378.41168.1971371.8321233.0961117.8751159.7631152.578988.725671.348657.926684.531662.527510.525445.507535.25505.723369.37409.103488.493410.813416.283355.186194.135395.88303.689NANANANA
us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax ▅▃█▇▅▂▇█▄▄▄▅▁▆▅▆█▅▂▄▃▅▃▄▇▁▃▂▄▅▅▆▅▄▆▆▃▆▃▃▆15.9-48.589.050.916.9-63.952.579.4-10.3-17.8-29.08.5-92.044.712.043.982.820.0-75.8-14.4-58.09.6-35.078-23.50463.035-100.853-37.972-60.254-8.047-2.94419.81133.5648.056-24.41924.2125.093-51.22625.154-50.113-50.50522.235NANANANANANANANANA
us-gaap:OtherComprehensiveIncomeLossNetOfTax ▃▅▁▂▂▂▂▆▂▃▃▃▃▃▃▃▂▂▆▂▂▂█▁▂▂▃▂▂▃▃▃▃▂▂▃▂▃▂▂▃2.4125.4-73.4-45.4-30.6-13.5-42.9160.6-33.520.67.513.342.313.08.09.4-13.6-5.3172.7-18.1-23.5-35.3262.428-56.391-30.487-11.0541.985-11.309-4.3225.3891.5725.8212.839-12.67-4.189-0.56-32.8478.891-34.084-18.94829.623NANANANANANANANANA
us-gaap:OtherNonoperatingIncomeExpense ▇████▇▆▇▇█▇▇▇▇▇▇▇█▁▇▇▇▄▇▇▇▇▇█▇▇▇▇▇▇▇██▇▇▇█▇▇█▇████-3.00.12.50.74.2-4.4-36.0-3.7-7.1-0.2-1.7-3.2-3.8-1.8-4.9-5.1-5.82.7-203.1-4.4-5.5-4.4-116.6-2.0-8.2-14.986-8.751-16.294.861-5.601-5.405-4.64-10.428-14.457-14.29-4.5482.9515.144-3.973-7.727-11.7289.951-4.7-6.91.0-8.46.49.414.76.8
us-gaap:ProfitLoss ▆▃▃▄█▇▇██▇▅▇▅▆▁▆▅▅▄▆▆▅▅▆▅▅▅▅▅▄▃▄▄▃▃▃▃▃▃▃▃▃▃▂▃▃▃▃▂▃1025.5404.6357.6703.91606.51392.61439.71545.91494.11408.8944.91442.9915.01171.2-166.31226.1862.8747.5647.91030.21048.4969.2828.71019.493924.825820.174882.6856.12723.132479.728457.3487.616490.67426.749292.1398.4387.141302.366300.2353.662304.049308.766271.8112.2294.6220.0306.0279.6144.9246.6
us-gaap:RealizedInvestmentGainsLosses ▆▁▅▄▆▄▃▅▃█153.9-436.664.7-82.1106.8-77.3-148.9-4.1-173.4376.4NA141.15.3-14.4NA-4.0-13.4NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ResearchAndDevelopmentExpense us-gaap:TypeOfArrangement biib:DenaliTherapeuticsInc▁█0.041.3NA41.3NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ResearchAndDevelopmentExpense us-gaap:TypeOfArrangement biib:SageTherapeuticsIncNANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost ▂▂█▅▃▂▃▂▂▂▃▂▄▂▂▂▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁585.1514.21726.11140.9647.6476.3691.7540.4484.8563.7611.6507.9981.0496.7587.6446.4796.2423.4533.9529.0473.1437.3541.66519.863490.728460.549500.091417.174447.273528.884422.233410.017327.463284.34345.181304.217329.559NANANANANANANANANANANANANA
us-gaap:Revenues ▆▅▆▇█████▇█▇▇▇▇▆▆▆▆▆▆▅▆▆▅▅▅▅▅▄▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁2775.02694.02852.63376.13681.63534.33671.33600.13616.73489.83526.33439.03356.53131.13307.03077.83078.42810.72872.02955.82894.22726.82839.32777.8592591.6422554.9632640.72511.4462421.4522129.7511965.91827.781723.4731415.0961417.91385.5541420.9511292.0141326.71309.9341208.6471203.3421219.01175.81212.71108.91127.01120.51093.31036.5
us-gaap:SellingGeneralAndAdministrativeExpense ▆▅█▅▅▅▆▅▅▅▅▄▄▄▅▃▃▄▄▄▄▄▅▄▄▅▅▅▅▄▄▃▃▂▃▂▂▂▁▁▁▁▁▁▁▁637.3595.0806.2573.1555.1570.1664.9554.5587.6567.7591.1497.7516.2501.3572.4433.8430.2499.1495.5462.7492.4497.3583.017477.827491.895560.361573.61570.436576.622511.674522.857405.584431.012352.598375.977299.631301.767300.089283.916261.398266.301244.516276.393244.16262.322248.664NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:Assets ▇▇▇▇▇█████▇▇▇▇▇▆▆▆▆▆▆▆▅▆▄▄▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁▁24470.423854.724618.924934.125511.826119.227234.327484.026287.626445.525288.925492.223952.926090.123652.623073.221759.021195.922876.822104.921514.820674.719504.820728.36816759.17115219.45414316.55913704.14212917.99812230.13111863.33511250.24910841.5910164.71710130.1189630.6219162.389113.5499049.6048802.2048621.9798293.5248092.493NANANA8551.854NANANA
us-gaap:Liabilities ▇▇██████▇▇▇▇▆▇▆▆▆▅▆▅▆▆▆▆▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁13255.613191.513932.814189.614222.613582.313895.213492.213338.812623.512257.311732.411699.212052.611054.510224.310185.49728.510748.29990.110111.110346.610129.910161.4254186.1733549.9963502.5193273.2573352.7723089.0683242.4973124.5612939.4452825.1113166.3232968.6812891.6952805.0012622.6172568.612565.7852619.2242643.05NANANA2289.972NANANA
us-gaap:LiabilitiesAndStockholdersEquity ▇▇▇▇▇█████▇▇▇▇▇▆▆▆▆▆▆▆▅▆▄▄▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁▁24470.423854.724618.924934.125511.826119.227234.327484.026287.626445.525288.925492.223952.926090.123652.623073.221759.021195.922876.822104.921514.820674.719504.820728.36816759.17115219.45414316.55913704.14212917.99812230.13111863.33511250.24910841.5910164.71710130.1189630.6219162.389113.5499049.6048802.2048621.9798293.5248092.493NANANA8551.854NANANA
us-gaap:StockholdersEquity ▅▅▅▅▆▇▇█▇█▇█▇█▇▇▆▆▆▆▆▅▄▅▇▆▅▅▄▄▄▃▃▃▂▂▂▂▂▂▁▁▁10751.910682.210700.310758.511308.712546.913343.213995.912952.913829.913039.613766.612260.914053.712612.812860.511585.211479.012140.112117.511403.810326.89372.810572.72612572.57711666.77110809.0110427.6969561.2999136.7118620.2428125.0927901.5497339.016961.5236659.5526268.2976305.9016425.4996229.1485977.055604.1595396.506NANANA6221.53NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:AssetsCurrent ▅▅▅▆▆▆▆▆▆▇▆▇▅█▆▆▅▅▇▆▅▅▅▇▄▃▃▃▂▂▂▁▁▄▂▁▁▁▁▁▁▁▁7183.76719.56887.17843.18493.88007.28381.88448.27909.88942.67640.98719.07432.110195.47873.37568.07108.76859.78732.28091.87447.77201.36700.39270.8735618.9855258.8964672.6734372.1113925.0133525.0243184.9342643.6722523.2215328.8383244.3373055.3882868.9192677.952975.4272837.2882688.6232628.3152540.42NANANA2480.595NANANA
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents ▃▁▁▅▆▇█▆▃▅▁1742.01217.51331.22224.82384.92591.32913.72343.91723.42243.21224.6NANANA1573.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:AccountsReceivableNetCurrent ▆▇▇███▇▇▇█▇▇▇▇▆▅▆▅▅▅▄▅▄▄▄▅▄▃▃▃▂▂▂▂▁▁▁▁▁▁▁▁▁1688.01854.31913.82024.92133.62092.61880.51933.51959.62088.91958.52017.31951.01939.21787.01567.51630.21501.51441.61467.81293.01395.11227.01327.781310.8211389.9951292.4451091.2321002.3281018.487824.406891.396861.457753.611686.848661.519683.841684.242584.603581.052666.96687.609605.329NANANA551.208NANANA
us-gaap:InventoryNet █▇▇▆▆▅▅▄▄▄▆▅▆▅▅▆▆▆▆▆▆▆▅▆▅▅▅▄▄▄▄▃▃▂▂▂▁▁▁▁▁1254.81171.81068.61027.7952.7858.8804.2751.8776.7770.2929.9916.6931.7890.8902.71007.2936.5921.61001.61009.7996.4964.6893.4918.921865.738825.349804.022753.063715.935672.75659.003614.483570.39506.557447.373392.936362.94337.619326.843310.934308.254NA289.066NANANANANANANA
us-gaap:OtherAssetsCurrent ▅▅▆▅▄▅▄▅▆▆▅▆▆▆▆▆▇█▇▆▇▆▆▆▅▄▃▃▂▂▂▂▁▁▁▁▁▁▁▁▂▁▂767.9786.1881.1683.5638.8683.8631.0743.2980.4965.4687.6848.3843.3895.9962.0967.01146.11231.91093.3993.11027.4941.1836.9861.882750.039579.599447.462396.471346.787295.26226.134205.635173.708169.939136.011126.174149.247122.126144.6194.199201.794186.291215.822NANANA177.924NANANA
us-gaap:Land NANA119.8NANANA118.1NANANA144.5NANANA141.2NANANA137.8NANANA74.7NANANA56.9NANANA59.7NANANA55.754.0NANA51.9NANANA107.6NANANA111.2NANANA
us-gaap:MachineryAndEquipmentGross NANA1027.8NANANA844.5NANANA1258.1NANANA1207.7NANANA1105.8NANANA1079.6NANANA1011.3NANANA944.5NANANA882.0824.3NANA570.1NANANA576.0NANANA534.0NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:NoncurrentAssets NANA3844.8NANANA3674.3NANANA3601.2NANANA3182.4NANANA2501.8NANANA2187.6NANANA1765.7NANANA1750.7NANANA1742.2NANANA1838.4NANANA1826.2NANANA1805.4NANANA
 us-gaap:NoncurrentAssets us-gaap:StatementGeographical biib:SegmentGeographicalGroupsOfCountriesGroupOtherNANA10.9NANANA12.0NANANA1.8NANANA2.1NANANA1.4NANANA1.7NANANA3.2NANANA3.3NANANA2.2NANANA2.4NANANA1.6NANANA2.1NANANA
 us-gaap:NoncurrentAssets us-gaap:StatementGeographical biib:SolothurnNANA2180.6NANANA2028.8NANANA1748.5NANANA1215.7NANANA545.5NANANA161.5NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NoncurrentAssets us-gaap:StatementGeographical country:USNANA1496.3NANANA1493.2NANANA1152.7NANANA1226.9NANANA1272.3NANANA1296.5NANANA1055.5NANANA984.4NANANA996.6NANANA1012.5NANANA1100.3NANANA1092.7NANANA
 us-gaap:NoncurrentAssets us-gaap:StatementGeographical srt:AsiaNANA16.2NANANA6.2NANANA3.9NANANA5.2NANANA7.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NoncurrentAssets us-gaap:StatementGeographical srt:EuropeNANA2321.4NANANA2162.9NANANA2442.8NANANA1948.2NANANA1221.1NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:PropertyPlantAndEquipmentGross NANA5193.8NANANA4838.2NANANA5398.6NANANA4741.5NANANA3941.1NANANA3517.7NANANA2952.1NANANA2869.0NANANA2683.32574.9NANA2353.5NANANA2408.8NANANA2279.6NANANA
 us-gaap:PropertyPlantAndEquipmentGross biib:FacilityLocation biib:SolothurnNANA256.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:PropertyPlantAndEquipmentGross biib:FacilityLocation biib:SolothurnSwitzerland1300.0NANA256.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:FurnitureAndFixturesGross NANA62.5NANANA58.3NANANA61.6NANANA55.3NANANA60.6NANANA72.9NANANA64.3NANANA60.3NANANA46.943.1NANA37.6NANANA54.5NANANA50.7NANANA
us-gaap:LeaseholdImprovementsGross NANA104.6NANANA99.5NANANA94.4NANANA80.6NANANA123.7NANANA166.6NANANA155.5NANANA139.6NANANA107.3105.8NANA102.7NANANA100.8NANANA73.1NANANA
us-gaap:ConstructionInProgressGross NANA1950.8NANANA2084.4NANANA1758.5NANANA1276.0NANANA658.6NANA158.0441.2NANANA168.6NANANA144.2NANANA212.3242.1NANA553.6NANANA506.9NANANA506.7NANANA
 us-gaap:ConstructionInProgressGross biib:FacilityLocation biib:SolothurnNANA1800.0NANANA1900.0NANANA1600.0NANANA1200.0NANANA481.5NANANA99.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ConstructionInProgressGross biib:FacilityLocation biib:SolothurnSwitzerland▃███▇▇███▇▇▇▆▅▅▄▃▃▂▁▁618.41900.01800.01800.01700.01700.01900.01800.01800.01700.01600.01600.01500.01300.01200.0968.8798.1609.8481.5350.8247.8NA99.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment ████▇▇▇▇████▇▇▇▇▇▇▇▇▇▇▇▇▆▆▆▆▆▆▆▆▆▆▆▁▅▅▅▅▅▅▅1880.31827.61782.31734.81687.01636.71590.91555.31886.21841.01797.41730.61671.71631.51559.11580.61511.41438.11439.31528.41471.01394.41330.11320.51274.21217.81186.41246.41210.61163.91118.31074.01030.4983.8941.1-898.3854.7821.5782.1749.1771.1789.9767.2NANANA642.5NANANA
us-gaap:AmortizationOfIntangibleAssets NANA58.863.361.571.5-148.2283.970.168.2-112.0281.9107.4103.9139.8108.9117.5448.5104.299.792.988.896.62898.06592.00495.903107.246122.431116.826143.258109.42499.99882.22551.30150.94853.01352.28245.96150.86749.34755.13653.21653.3653.53153.14848.889NANANANA
us-gaap:PropertyPlantAndEquipmentNet ▇▇▇▇▇▇▇▆▆▆██▇▇▇▆▅▅▄▄▄▃▃▃▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁3442.23438.33411.53359.93330.73281.63247.33138.13077.53013.83601.23538.93409.03334.73182.42995.92827.62610.92501.82387.02301.82258.92187.62027.8211837.671739.6281765.6831724.1291756.1641744.2661750.711806.0741787.7761736.8111742.2261676.5831622.8121617.4591571.3871572.2591712.8691673.5021641.634NANANA1637.083NANANA
us-gaap:Goodwill ████████████▇▇▆▆▅▅▅▄▄▄▃▃▃▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁5763.95763.15762.15755.75751.05752.05757.85746.15749.25639.75706.45440.15170.34907.84632.54127.53870.43611.73669.33419.73167.12917.92663.82408.8542154.3411849.8521760.2491541.2041364.8151232.9161232.9161210.7181210.7181210.7181201.2961204.741197.9041193.2791146.3141146.3141146.3141146.3141146.314NANANA1138.621NANANA
 us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill biib:Researchanddevelopmentasset,us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass biib:BIIB111,us-gaap:InProcessResearchAndDevelopment▁█15.0365.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill biib:Researchanddevelopmentasset,us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass biib:BIIB112,us-gaap:InProcessResearchAndDevelopment▁█28.4220.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill biib:Researchanddevelopmentasset,us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass biib:TGN,us-gaap:InProcessResearchAndDevelopment▁▁█▆▅▅136.0135.1177.5167.6160.2161.7NANANANANA41.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass us-gaap:InProcessResearchAndDevelopment▁▅▅▆▆▆▇▆█▃▃▃▄▅▅▅▄▄▄▅▅▅▅▅▅▅▂▂▂▂▂▂▂179.4720.1762.5943.0954.9956.5965.5954.81175.6480.5476.0480.9670.5696.4680.6680.6668.6653.7648.0679.7692.3718.5730.5735.6752.0726.1314.1314.1330.9330.9327.4327.4327.4NA330.1NANANANANANANANANANANANANANANA
us-gaap:IntangibleAssetsNetExcludingGoodwill ▃▄▄▅▅▅▅▅▆▄▄▅▆▆▆▇▇▇▆▆▆▆▇▇▇▇▇▇▇▇███▁▁▁▁▁▁▁▁▁▁2385.02988.13084.33323.63383.83446.93527.43392.43681.33056.23120.03379.03661.33794.53879.64019.44051.34103.93808.33869.93967.64012.24085.14181.2454294.7914353.1234028.5074129.7544249.3784364.3844474.6534580.1994678.8841581.5111631.5471681.2321732.9721783.9811608.1911659.1141678.8671731.8441772.826NANANA1871.078NANANA
us-gaap:FiniteLivedIntangibleAssetsNet NANA2257.8NANANA2497.9NANANA2580.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA0.0NANANANANANANANANANANA
 us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass biib:OutLicensedPatents▇▇▇▇███▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂2141.62204.02257.82316.62364.92426.42497.90.80.90.91.01.73.45.57.710.613.516.719.723.928.432.837.343.449.455.561.669.577.485.0127.2134.7142.1149.5157.0164.4171.8179.3186.7196.9207.1NA227.8NANANANANANANA
us-gaap:DeferredTaxAssetsLiabilitiesNet 500.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OperatingLeaseRightOfUseAsset ▇▇████████▁402.5414.5433.3434.2436.2422.0427.0422.0434.4447.80.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherAssetsNoncurrent ▇▇█▅▄▃▄▄▄▅▅▃▃▁▃▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁2528.12423.02899.01834.91483.31130.61252.81238.81306.01898.31690.61009.8902.1380.11027.51300.41268.31184.51335.81239.61153.01094.61107.6892.221751.588640.63618.795565.513611.791639.269594.35636.028533.852306.839274.054271.144271.864368.937331.548237.87211.747228.105248.198NANANA230.397NANANA
us-gaap:EquitySecuritiesFvNi NANA1974.3NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:EquitySecuritiesFvNi us-gaap:FinancialInstrument biib:EquitySecuritiesCurrent█▇▁1593.51442.886.5NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:EquitySecuritiesFvNi us-gaap:FinancialInstrument biib:EquitySecuritiesNonCurrent▃▁█1593.51442.81887.8NANANA337.5NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:AccountsPayableCurrent ▅▆▇▆▅▅█▅▅▅▅▄▄▅▅▄▄▄▃▃▂▃▃▃▃▂▂▂▂▂▂▁▁▁▂▁▁▁▂▁▁▁▁375.3430.4454.9398.4383.9389.0530.8382.2377.1378.0370.5342.3295.7345.8395.5298.7330.3316.4279.8274.0225.9271.3267.4251.228282.702236.128229.178233.629224.931212.809219.913166.709163.094165.207203.999157.424159.152173.33186.448159.197170.746159.136162.529NANANA118.534NANANA
us-gaap:LiabilitiesCurrent ▅▅▆▆▆██▇▅▅▅▅▅▅▅▆▅▅▅▄▄▄▄▄▄▃▃▃▃▂▃▂▂▂▂▂▂▂▁▁▁▁▁3347.23165.83742.23804.03447.14638.64863.84432.23210.93148.73295.23174.93152.43152.13368.23448.43379.72992.53419.92499.72516.22776.62577.72633.9682555.8321946.2312219.7061940.6471916.6241594.2471758.2791518.7111304.0741281.6621657.3891521.0931432.8651337.319912.889885.346954.33978.8461050.122NANANA714.942NANANA
 us-gaap:OperatingLeaseLiabilityCurrent us-gaap:BalanceSheetLocation us-gaap:AccruedLiabilitiesNANA83.2NANANA73.6NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherAccruedLiabilitiesCurrent ▄▄▅█▅▄▄▄▄▄▃▄▄▄▄▃▃▂▄▃▃▃▃▃▂▂▂▁▁760.3700.1791.41274.8774.1662.0726.7677.4727.5708.0609.3640.0638.1653.4636.9606.1591.2475.0685.7566.8613.4582.0579.6549.2433.3403.5456.8276.2263.7NA285.6NANANANANANANANANANANANANANANANANANANA
us-gaap:OtherLiabilitiesCurrent ▇▆██▆▆▇▆▅▆▇▆▆▆▇▆▆▅▇▅▅▅▅▄▄▃▄▃▃▃▃▃▂▂▂▂▁▁▁▁▁▁▁2741.02592.33145.33286.22486.52437.82765.82429.12318.02435.02861.22578.52633.72571.12901.32455.22436.92044.62903.52012.02072.72003.92096.81918.8971812.0991384.7741819.3341544.161495.5491216.8431355.1871204.4371056.229885.093979.945866.208762.353660.562677.21674.743641.273591.448665.923NANANA500.755NANANA
us-gaap:TaxesPayableCurrent ▄▃▃▂█▅▂▂▆▄▂▄▄▄▂▂▂▂▄▃▄▇▃▇▇▅▃▃▃▃▃▃▂▁▁▁▂▁▁▁▁▂▂230.9143.1142.0119.4576.7310.071.4125.6427.2238.563.5254.1223.0231.968.2121.352.670.0231.9208.8212.8496.5208.7458.672457.769322.075168.058159.638192.758161.045179.685144.1881.56328.04520.06644.25258.31550.06645.93947.98410.3393.48384.517NANANA75.891NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:LongTermDebt █████▅▅▅▆▆▆▆▆▆▆▆▆▆▇▇▇▇▇▇▁▁▁▁▁▁▁▁▁7269.27267.27426.27425.07423.84459.94459.04458.25948.55943.25936.55931.15928.45929.45935.05938.35954.05952.76512.76529.66538.36535.66521.56529.275576.207580.672582.061583.977586.091591.012592.433694.894726.388NA687.396NANANANANANANANANANANANANANANA
us-gaap:DeferredIncomeTaxLiabilitiesNet ▁▁▁▂▃██918.9966.71032.81123.41461.52722.82810.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:MinorityInterest █▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂462.9-19.0-14.2-14.0-19.5-10.0-4.1-4.1-4.1-7.9-8.0-6.8-7.2-16.2-14.7-11.6-11.6-11.6-11.5-2.7-0.11.32.1-5.7830.4212.6875.033.1893.9274.3520.5960.5960.5960.5962.2722.3882.3882.6471.4884.44679.14470.14152.93739.540.441.240.352NANANA
us-gaap:OtherLiabilitiesNoncurrent ▆▇▆▇▇▆▆▇▆▆▇▇▇██▃▃▃▃▄▄▄▄▄▄▄▃▃▃▃▃▃▂▃▂▂▂▂▁▁▁▁▁1356.41411.81329.61428.11475.41357.31348.91370.91355.81353.81389.41511.81457.61640.01628.7716.9750.9688.8722.5862.1951.0916.6905.8861.421915.731892.529650.096658.276710.965702.908659.231608.473595.642674.951604.266539.569534.358517.406400.276384.45351.685356.261325.599NANANA254.205NANANA
us-gaap:OperatingLeaseLiabilityNoncurrent ▇▇▇██▇████▁363.9380.0402.0409.1414.8403.7412.7410.5423.0436.10.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo NANA93.5NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree NANA82.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour NANA75.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive NANA56.9NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive NANA129.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:StockholdersEquity ▅▅▅▅▆▇▇█▇█▇█▇█▇▇▆▆▆▆▆▅▄▅▇▆▅▅▄▄▄▃▃▃▂▂▂▂▂▂▁▁▁10751.910682.210700.310758.511308.712546.913343.213995.912952.913829.913039.613766.612260.914053.712612.812860.511585.211479.012140.112117.511403.810326.89372.810572.72612572.57711666.77110809.0110427.6969561.2999136.7118620.2428125.0927901.5497339.016961.5236659.5526268.2976305.9016425.4996229.1485977.055604.1595396.506NANANA6221.53NANANA
us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest ▆▅▅▅▆▇▇█▇█▇█▇█▇▇▆▆▆▆▆▅▄▅▇▆▅▅▄▄▄▃▃▃▂▂▂▂▂▂▁▁▁11214.810663.210686.110744.511289.212536.913339.113991.812948.813822.013031.613759.812253.714037.512598.112848.911573.611467.412128.612114.811403.710328.19374.910566.94312572.99811669.45810814.0410430.8859565.2269141.0638620.8388125.6887902.1457339.6066963.7956661.946270.6856308.5486426.9876233.5946056.1945674.35449.443NANANA6261.882NANANA
us-gaap:CommonStockValue ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▇█████████████████▇▇0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.1240.1290.1290.1290.1290.1280.1280.1280.1280.1280.1280.1270.1270.1270.1290.1280.1280.1270.1250.124NANANA0.144NANANA
us-gaap:RetainedEarningsAccumulatedDeficit ▆▆▆▆▇▇██▇███▇█▇▇▇▇▇▇▇▆▆▆▅▅▄▄▄▃▃▃▃▂▂▂▂▂▂▁▁▁▁13900.713833.513976.313961.014466.715673.116455.417065.216182.817026.716257.016944.115499.517334.615810.416107.714881.714781.215071.615030.014229.113179.312208.411999.35811033.73610106.469283.9198400.4557543.5976829.0916349.1355891.8295404.2134913.5434486.7944194.5513796.1543409.3083106.7612806.5232454.8482166.8131872.481NANANA1068.89NANANA
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▄▄▂▃▄▅▅▆▃▃▃▃▂▂▁▁▁▁▁▂▂▃▃▄▆▆▆▇▇▇▇▇▆▆▆▇▇▇▇██▇▇-171.8-174.3-299.0-225.5-181.0-149.3-135.2-92.3-252.9-219.8-240.4-248.3-261.6-303.9-318.4-329.4-338.8-325.2-319.9-300.9-282.8-259.3-224.0-157.416-101.025-70.538-59.488-37.987-26.678-22.355-27.745-29.315-55.136-67.975-55.305-51.115-50.557-17.71-26.5357.57125.713-0.992-21.61NANANA50.496NANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedDefinedBenefitPlansAdjustment▁▁▁▆▆▆▆▆▆▆▆▅▅▅▅▆▆▆▆▅▅▅▅▇▇▆▆████████-63.9-64.3-66.3-32.4-31.9-32.0-32.8-29.8-30.6-30.7-31.3-36.6-36.4-37.3-36.8-33.2-33.2-32.6-32.7-36.5-36.9-37.6-37.8-27.0-27.5-30.3-31.6-18.3-19.0-18.8-19.6-18.5-19.4-20.5-21.7NANANA-9.0NANANA0.2NANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedGainLossNetCashFlowHedgeParent▅▅▁▃▆▇▆█▆▇▇▆▆▂▃▃▄-40.4-29.4-179.0-93.3-9.641.67.872.813.751.634.74.5-0.7-133.5-104.5-104.5-69.0NA57.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss▄▄▄▅▅▃▅▆▆▅▃▄▄▄▄▃▃▁▁▄▆▅▄▄▄▄▄▄▄▆▆█▆▅▅0.10.61.45.25.1-3.64.26.36.22.9-4.0-1.9-1.7-2.3-1.6-4.2-5.2-12.4-10.80.86.21.7-0.8-1.60.70.9-0.40.50.47.35.615.49.23.14.2NANANA0.0NANANA12.4NANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedOtherComprehensiveIncomeNANA-299.0NANANA-135.2NANANA-240.4NANANA-318.4NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest▃▄▁▆▇█▅█▅▄▂▂▂▂▂11.613.9-8.530.641.948.125.150.429.217.53.50.00.00.00.0NANANA0.0NANANA0.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedTranslationAdjustment▆▆▇▅▄▄▅▄▂▂▃▃▃▅▄▄▃▁▁▃▃▄▄▅▅▄▆▇████▇▇▇-79.2-95.1-46.6-135.6-186.5-203.4-139.5-192.0-271.4-261.1-243.3-214.3-222.8-130.8-175.5-187.5-231.4-314.2-334.2-258.4-244.0-186.0-195.6-160.5-137.0-200.1-99.2-61.2-1.07.110.0-9.9-43.5-51.5-27.1NANANA-50.3NANANA-24.4NANANANANANANA
us-gaap:TreasuryStockValue ██████████████████▇▇▇▇▇▇▇▇▇▆▆▅▅▅▄▄▄▄▄▄▂▂▂▁▁2977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12977.12611.72611.72611.72611.72611.72611.7132611.7062611.7062611.7062084.9082061.8321724.9271724.9271724.9271365.6411365.6411324.6181303.0741303.0741303.074839.903728.503728.503537.215349.592NANANA679.92NANANA
us-gaap:MinorityInterest █▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂462.9-19.0-14.2-14.0-19.5-10.0-4.1-4.1-4.1-7.9-8.0-6.8-7.2-16.2-14.7-11.6-11.6-11.6-11.5-2.7-0.11.32.1-5.7830.4212.6875.033.1893.9274.3520.5960.5960.5960.5962.2722.3882.3882.6471.4884.44679.14470.14152.93739.540.441.240.352NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▆▄▁▆█▇█▇█▆█▇▅▆▇▇▆▃▇▅▅▅▅▅▅▄▅▅▅▂▅▄▄▃▄▄▄▃▄▄▃▃▃▃▃▃1227.3769.0-367.11181.11948.51467.31960.21694.91964.01459.51895.41735.91099.31457.11518.31628.31169.2235.21576.6986.6995.8963.41040.395895.4481047.22733.037932.863914.033990.593104.626869.005671.922625.212178.939507.907541.784635.581194.625473.974570.523429.666253.578431.056428.241428.481336.895NANANANA
us-gaap:NetCashProvidedByUsedInInvestingActivities ▅▅▅▅▃▆▇▄▅▆▁▄▂█▃▂▅▃▄▅▃▂▁▃▂▄▄▄▄▅▃▄▃▅▄▄▅▅▄▄▄▅▄▅▇▆-152.7-64.7-166.4-52.4-832.7442.9708.4-365.9-110.8238.8-1625.3-619.1-1148.51346.6-769.5-1246.8-202.6-744.2-581.736.2-736.1-1203.2-1807.529-989.937-1253.363-502.771-378.278-540.564-630.1275.993-709.976-324.392-726.241155.941-375.454-522.39-53.1160.618-389.532-587.177-546.79-126.795-518.622-69.754683.964249.737NANANANA
us-gaap:NetCashProvidedByUsedInFinancingActivities ▄▃▄▃▃▂▂▄▂▄▃▄▁▄▄▄▄▃▄▄▄▄▂█▄▅▄▄▄▅▄▄▄▄▄▄▄▄▄▄▄▄▅▄▃▄-564.5-785.0-401.1-1312.9-1313.4-2245.3-2116.4-689.0-2375.7-679.3-1437.025.1-2791.5-268.6-708.1-19.5-751.0-901.4-721.2-300.6-13.447.4-1998.4032907.584-3.53780.756-513.265-35.123-322.36114.87511.181-318.522-170.763-238.424-15.524-28.25-417.44-416.264-142.809-99.12821.907-99.832225.926-461.259-1026.126-523.46NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:DeferredIncomeTaxExpenseBenefit ▁▆▆▆▇▆▆▆▅█▇▆▅▇▇▆▅▇▅▆▆▆▆▅▅▆▅▅▆▅▅▆▆▆▆▆▆▆▆▇▆▇▆▆▆▆-607.8-15.0-62.931.7143.336.938.7-43.2-156.4228.0153.112.6-110.553.1131.4-19.2-96.676.1-118.2-26.6-39.18.940.202-95.155-107.38616.739-78.949-82.767-66.948-79.558-78.89-48.14-51.522-66.525-30.042-43.027-39.955-3.87637.87867.072-23.34871.974-20.166-30.927-38.3598.042NANANANA
us-gaap:DepreciationDepletionAndAmortization ▁▂▁▂▂▂▂▅▂▂▅▅▃▃▁▃▅█▃▃▃▂▂▂▂▂▂▃▂▃▂▂▂▁▁▁72.9146.990.4134.0112.9119.9113.0329.5117.0121.1329.7346.5171.5168.989.0177.4302.6512.0177.4180.2175.4149.7156.3151.577144.586147.937157.642175.406164.139190.963158.383147.477128.42797.45396.87694.203NANANANANANANANANANANANANANA
us-gaap:IncreaseDecreaseInAccountsReceivable ▁▃▂▂▄█▃▄▂▆▃▅▅▆█▃▆▇▄▇▂▇▂▄▂▆█▆▄▇▂▅▆▅▄▃▃▅▅▃▃▅▄▅▄▄-174.3-37.2-138.5-133.130.4238.4-71.2-0.5-133.7136.6-48.866.853.2134.0209.8-75.4105.5195.73.3173.1-95.0160.0-92.60824.701-89.38128.287215.332108.096-8.724197.685-93.10734.172110.14275.54614.915-29.244-78.30889.06656.04-37.575-35.80390.71226.50849.7642.75420.201NANANANA
us-gaap:IncreaseDecreaseInInventories ▇█▆▇█▆▆▆▅▁▅▄▆▄▂▇▆▆▅▅▆▇▅▆▆▅▆▆▆▅▆▆▆▆▆▆▅▅▅▅▅▅▅▅▄▄81.3112.545.782.4126.062.266.561.420.3-129.020.2-8.242.7-2.6-75.885.039.146.210.526.839.788.624.01369.09359.78721.50766.02747.20155.70916.9861.14653.64368.36260.80957.88638.0625.33619.02723.45211.05918.216.49820.8385.136-9.183-12.264NANANANA
us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet ▅▆▁▇▅▅▅▅▄█▄▇▅▆▅▆█▆▆▅▅▅▄▆▅▆▆▄▅▆█▃▅▅▅▅▆▆▄▅▆▅16.480.9-273.7106.98.6-18.52.3-19.3-90.8171.1-86.789.7-28.720.0-18.262.9153.034.348.2-12.0-35.3-14.8-90.55955.285-3.33769.71153.601-66.835-31.40775.338182.535-129.402-33.654-35.2127.282-38.26250.61520.036-53.648-9.34575.896-6.638NANANANANANANANA
us-gaap:NetCashProvidedByUsedInOperatingActivities ▆▄▁▆█▇█▇█▆█▇▅▆▇▇▆▃▇▅▅▅▅▅▅▄▅▅▅▂▅▄▄▃▄▄▄▃▄▄▃▃▃▃▃▃1227.3769.0-367.11181.11948.51467.31960.21694.91964.01459.51895.41735.91099.31457.11518.31628.31169.2235.21576.6986.6995.8963.41040.395895.4481047.22733.037932.863914.033990.593104.626869.005671.922625.212178.939507.907541.784635.581194.625473.974570.523429.666253.578431.056428.241428.481336.895NANANANA
us-gaap:NetIncomeLoss ▄▄▃▅█▇███▇▆█▅▇▁▇▅▅▅▆▆▆▅▆▆▅▅▅▅▄▄▄▄▄▃▄▄▃▃▃▃▃▃▃▃▃▃▃▃▃448.5410.2357.9701.51542.11399.11439.71545.91494.11408.8946.81444.4866.61172.9-297.41226.1862.8747.6649.21032.91049.8970.9831.6965.622927.276822.541883.5856.858714.506479.956457.3487.616490.67426.749292.1398.4386.846302.661300.2351.826288.034294.331240.3254.1293.4217.4305.6277.7142.8244.0
us-gaap:ProfitLoss ▆▃▃▄█▇▇██▇▅▇▅▆▁▆▅▅▄▆▆▅▅▆▅▅▅▅▅▄▃▄▄▃▃▃▃▃▃▃▃▃▃▂▃▃▃▃▂▃1025.5404.6357.6703.91606.51392.61439.71545.91494.11408.8944.91442.9915.01171.2-166.31226.1862.8747.5647.91030.21048.4969.2828.71019.493924.825820.174882.6856.12723.132479.728457.3487.616490.67426.749292.1398.4387.141302.366300.2353.662304.049308.766271.8112.2294.6220.0306.0279.6144.9246.6
us-gaap:ShareBasedCompensation ▆█▅▂▅█▃▄▅▄▃▃▃▄▂▂▂▃▃▂▃▄▂▃▄▅▃▃▃▄▂▃▂▃▂▂▂▂▁▂▁▂▂▃▄▅54.170.049.033.548.167.738.445.952.345.738.537.338.343.430.630.130.337.037.033.738.845.329.86337.8641.61452.06335.79435.65237.51646.3431.44237.46430.6336.75730.18827.91128.07132.39626.3829.22624.2833.11933.23239.22444.36451.006NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ▅▅▅▅▃▆▇▄▅▆▁▄▂█▃▂▅▃▄▅▃▂▁▃▂▄▄▄▄▅▃▄▃▅▄▄▅▅▄▄▄▅▄▅▇▆-152.7-64.7-166.4-52.4-832.7442.9708.4-365.9-110.8238.8-1625.3-619.1-1148.51346.6-769.5-1246.8-202.6-744.2-581.736.2-736.1-1203.2-1807.529-989.937-1253.363-502.771-378.278-540.564-630.1275.993-709.976-324.392-726.241155.941-375.454-522.39-53.1160.618-389.532-587.177-546.79-126.795-518.622-69.754683.964249.737NANANANA
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▂▃▃▃▄▅▄▃▆▄█▆▆▇██▇▇▆▆▅▄▆█▄▃▄▂▂▂▃▃▂▁▂▂▂▂▂▂▂▁▂▁▂▁71.992.686.084.1105.0149.7110.490.1186.9127.1225.9163.2186.8194.7230.6229.1197.7210.0182.1170.3136.8126.9186.115229.197129.85897.83106.89762.54664.00254.30678.65380.18854.15133.28969.03758.06472.89654.55170.44251.34954.08632.14348.83538.9647.05138.209NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities ▄▃▄▃▃▂▂▄▂▄▃▄▁▄▄▄▄▃▄▄▄▄▂█▄▅▄▄▄▅▄▄▄▄▄▄▄▄▄▄▄▄▅▄▃▄-564.5-785.0-401.1-1312.9-1313.4-2245.3-2116.4-689.0-2375.7-679.3-1437.025.1-2791.5-268.6-708.1-19.5-751.0-901.4-721.2-300.6-13.447.4-1998.4032907.584-3.53780.756-513.265-35.123-322.36114.87511.181-318.522-170.763-238.424-15.524-28.25-417.44-416.264-142.809-99.12821.907-99.832225.926-461.259-1026.126-523.46NANANANA
us-gaap:ProceedsFromIssuanceOfLongTermDebt NANA0.10.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:PaymentsForRepurchaseOfCommonStock ▂▂▂▄█▆▆▃▇▃▄▁█▂▁▁▃▂▃▂▁▁▆█450.0600.0400.01250.02808.92220.22093.1717.92401.5655.81352.60.02750.0250.00.00.0781.8583.6651.1348.90.00.02001.812955.997NANA526.79823.076336.9050.00.001-359.30.041.02321.54453.22446.78463.171111.40.0191.288195.2870.0468.2451031.754577.58NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0124000.0129000.0129000.0129000.0129000.0128000.0128000.0128000.0128000.0128000.0128000.0127000.0127000.0127000.0129000.0128000.0128000.0127000.0125000.0124000.0144000.0
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Shares Issued

us-gaap:SharesIssued us-gaap:StatementEquityComponents

us-gaap:SharesIssued

us-gaap:CommonStock


Shares
Period End2020-12-312020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value1761911982052082192212252012342352382412572552540.255633248288297295
Percentage of SharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TreasuryStock


Shares
Period End2020-12-312020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value2323232323232323232323222222-19.641-17.655-0.013518-7.662-13.639-9.2070.0
Percentage of SharesIssued13.512.512.011.611.410.910.810.611.810.110.19.59.48.8-7.7-6.9-5.3-3.1-4.7-3.10.0

Common Stock Shares Issued

us-gaap:CommonStockSharesIssued

us-gaap:CommonStockSharesIssued


Common
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value1761982212352382412572552542550.24820.288494
Percentage of CommonStockSharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStockSharesOutstanding


Common
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value1521741972112152182342362362420.2405380.274855
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommonStockSharesOutstanding us-gaap:StatementEquityComponents

us-gaap:CommonStock


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value172174176177182191198205208219221
Percentage of CommonStockSharesOutstanding0.00.0115.60.00.00.0113.70.00.00.0112.1

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding


Weighted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value150152154157160173178184190197200201207211212211212215217219219219220232235235236236237237238238238238240241245244244242261272
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic


Weighted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value149151153156160172177184190196199201207211211211211215216218219218220232235234235236236236237237236236238239242242241239259269
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value3.02.72.334.479.68.18.18.47.857.174.747.174.185.55-1.415.84.073.473.04.724.794.443.774.163.943.53.753.633.022.031.942.062.071.81.241.681.621.261.241.451.191.221.01.061.130.81.070.960.490.85
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value2.992.692.324.469.598.088.088.397.857.154.737.154.185.54-1.45.794.073.462.994.714.794.433.774.153.933.493.743.623.012.021.922.052.061.791.231.671.611.251.221.431.181.20.991.051.120.81.060.950.490.84
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Allocated Share Based Compensation Expense

us-gaap:AllocatedShareBasedCompensationExpense

us-gaap:AllocatedShareBasedCompensationExpense


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312011-12-312011-09-302011-06-302010-12-312010-09-302010-06-30
Value-55.8-72.6-50.3-35.4-49.5-69.239475549404041466.3473636264249
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-2.0-2.7-1.8-1.0-1.3-2.01.11.31.51.41.21.21.21.50.52.83.02.23.64.1

us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType

biib:CashSettledPerformanceShares


Allocated
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-30
Value0.0-0.1-1.60.30.4-1.05.8-0.74.37.02.53.57.94.60.2-9.53.2
Percentage of AllocatedShareBasedCompensationExpense-0.00.22.30.60.7-2.014.4-1.79.20.00.00.00.00.00.00.00.0
Percentage of Revenues0.0-0.0-0.00.00.0-0.00.2-0.00.10.20.10.10.30.20.0-0.30.1
Percentage of Revenues biib:CashSettledPerformanceShares0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:EmployeeStockPurchasePlan


Allocated
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-30
Value3.36.93.15.62.31.73.44.61.92.13.91.72.13.62.72.53.72.93.0
Percentage of AllocatedShareBasedCompensationExpense-5.9-9.5-8.8-11.3-3.33.66.29.44.75.18.40.00.00.00.00.00.00.00.0
Percentage of Revenues0.10.30.10.20.10.00.10.10.10.10.10.10.10.10.10.10.10.10.1
Percentage of Revenues biib:EmployeeStockPurchasePlan0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:MarketStockUnits


Allocated
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-30
Value9.3165.57.4199.37.87.77.47.16.14.53.09.65.77.9137.39.1
Percentage of AllocatedShareBasedCompensationExpense-16.7-22.7-15.5-14.9-27.619.514.215.718.317.113.10.00.00.00.00.00.00.00.0
Percentage of Revenues0.30.60.20.20.50.30.20.20.20.20.20.10.10.30.20.30.50.30.4
Percentage of Revenues biib:MarketStockUnits0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:PerformanceStockUnitsSettledinCash


Allocated
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value3.46.04.1-4.08.91.30.91.01.10.30.10.00.00.0
Percentage of AllocatedShareBasedCompensationExpense-6.1-8.3-11.68.1-12.92.71.62.02.70.70.20.00.00.0
Percentage of Revenues0.10.20.1-0.10.30.00.00.00.00.00.00.00.00.0
Percentage of Revenues biib:PerformanceStockUnitsSettledinCash0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:PerformanceStockUnitsSettledinStock


Allocated
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value3.06.3-8.42.110-1.1122.01.31.40.70.00.00.0
Percentage of AllocatedShareBasedCompensationExpense-5.4-8.723.7-4.2-14.9-2.322.04.13.23.41.50.00.00.0
Percentage of Revenues0.10.2-0.20.10.3-0.00.30.10.00.00.00.00.00.0
Percentage of Revenues biib:PerformanceStockUnitsSettledinStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:TimeVestedRestrictedStockUnits


Allocated
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-30
Value40423534373731342930362627262833303031
Percentage of AllocatedShareBasedCompensationExpense-72.4-59.0-99.7-69.7-54.279.357.870.874.073.977.30.00.00.00.00.00.00.00.0
Percentage of Revenues1.51.61.00.91.11.10.91.00.90.91.20.90.91.01.01.21.11.11.2
Percentage of Revenues biib:TimeVestedRestrictedStockUnits0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:PerformanceShares


Allocated
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-30
Value0.00.0-0.10.20.30.53.02.0-0.83.21.24.59.11.36.9-2.81.2
Percentage of AllocatedShareBasedCompensationExpense-0.0-0.00.10.40.51.07.44.8-1.70.00.00.00.00.00.00.00.0
Percentage of Revenues0.00.0-0.00.00.00.00.10.1-0.00.10.00.20.30.00.3-0.10.0
Percentage of Revenues us-gaap:PerformanceShares0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AllocatedShareBasedCompensationExpense us-gaap:IncomeStatementLocation

us-gaap:Parent


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value46614032376135396638303933392929253330363336271933603940395145404640323129
Percentage of AllocatedShareBasedCompensationExpense-83.9-85.3-80.9-91.2-74.7-89.090.683.3120.979.274.997.080.984.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Revenues1.72.31.41.01.01.71.01.11.81.10.91.11.01.30.91.00.81.21.11.21.11.31.00.71.32.41.51.61.62.42.32.22.72.92.32.32.0
Percentage of Revenues us-gaap:Parent0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ResearchAndDevelopmentExpense


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value19331614153311152821152117211819171818222121201022352424242926202325181818
Percentage of AllocatedShareBasedCompensationExpense-34.2-46.3-33.6-41.2-30.7-48.130.232.251.144.337.652.042.546.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Revenues0.71.20.60.40.40.90.30.40.80.60.40.60.50.70.60.60.60.70.70.80.70.80.70.40.91.40.91.01.01.41.31.11.41.81.31.31.3
Percentage of Revenues us-gaap:ResearchAndDevelopmentExpense0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:SellingGeneralAndAdministrativeExpenses


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value404432253043313454272229252823231829273128342817265534343347403945
Percentage of AllocatedShareBasedCompensationExpense-72.2-61.8-65.4-70.6-61.2-62.379.971.599.656.755.872.860.961.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Revenues1.51.71.20.70.81.20.90.91.50.80.60.90.80.90.70.80.61.00.91.11.01.31.00.61.02.21.31.41.42.22.12.22.6
Percentage of Revenues us-gaap:SellingGeneralAndAdministrativeExpenses0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AllocatedShareBasedCompensationExpense us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-55.8-72.6-50.3-35.4-49.5-69.23947554940404146
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.599.5100.0100.0
Percentage of Revenues-2.0-2.7-1.8-1.0-1.3-2.01.11.31.51.41.21.21.21.5
Percentage of Revenues us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-55.8-72.6-50.3-35.4-49.5-69.2-39.4-47.8-55.049
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0-100.0-100.0-100.0100.0
Percentage of Revenues-2.0-2.7-1.8-1.0-1.3-2.0-1.1-1.3-1.51.4
Percentage of Revenues us-gaap:Parent0.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value45153428465715101385139617061461142995414579081185-286.4123584974263010141026935764909896811861845710485458513503414287397354311228334333332
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues16.319.910.019.541.039.238.047.440.441.027.142.427.137.9-8.740.127.626.421.934.335.534.326.932.734.631.832.633.729.322.823.328.129.229.320.328.724.924.117.325.627.627.6

Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value576-4.9-0.21.5-65.5-5.9-0.80.00.40.0881.5-48.41.7-131.10.00.00.11.42.61.41.72.853-53.5862.2662.2670.8790.738-8.6260.2280.00.00.00.0-0.130.00.295-0.23-74.3281.031817
Percentage of ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.00.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues20.8-0.2-0.00.0-1.8-0.2-0.00.00.00.02.50.0-1.40.1-4.00.00.00.00.00.10.00.10.1-1.90.10.10.00.0-0.40.00.00.00.00.0-0.00.00.0-0.0-5.60.11.61.4

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value102753028465815751379139617061460142995214569571184-155.3123584974262810121024933762962894809861844718485458513503414288397353311266334333332258136239189
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues37.019.710.019.542.839.038.047.440.441.027.042.328.537.8-4.740.127.626.421.934.235.434.226.834.734.531.732.633.629.722.823.328.129.229.320.328.724.924.120.125.627.627.621.211.619.717.1

Cost Of Goods And Services Sold

us-gaap:CostOfGoodsAndServicesSold

us-gaap:CostOfGoodsAndServicesSold


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value4594784904494114544474304766024884604214465093703661331331391391331391231001031009510697
Percentage of CostOfGoodsAndServicesSold100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues16.617.717.213.311.212.912.211.913.217.313.913.412.514.215.412.011.99.59.410.19.810.310.59.48.38.68.28.28.88.8

Cost Of Revenue

us-gaap:CostOfRevenue

us-gaap:CostOfRevenue


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value4594784904494114544474304766024884604214465093703661331331391391331391231001031009510697
Percentage of CostOfRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues16.617.717.213.311.212.912.211.913.217.313.913.412.514.215.412.011.99.59.410.19.810.310.59.48.38.68.28.28.88.8

Costs And Expenses

us-gaap:CostsAndExpenses

us-gaap:CostsAndExpenses


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value228917203183228917071714189317931660198720831741214315961841142418771786198515301433134816711406135814371485136314361462131511501066909987882915922917821797787863981816805
Percentage of CostsAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues82.563.8111.667.846.448.551.649.845.956.959.150.663.951.055.746.361.063.669.151.849.549.458.950.652.456.256.354.359.368.766.962.961.964.369.663.764.471.469.262.766.065.470.983.567.472.6

Gross Profit

us-gaap:GrossProfit

us-gaap:GrossProfit


Gross
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value23612927327030803224317031402887303729782935268527972707271224262493253825232413250724672305224223432208212918501707159314921281128412461281115811871186110811001118107911051011102710271002938
Percentage of GrossProfit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues82.886.788.887.187.888.186.882.786.186.687.585.884.688.088.186.386.885.987.288.588.388.889.087.888.787.987.986.986.887.286.690.690.689.990.289.789.590.691.791.491.891.891.291.291.291.791.790.5

Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value5824673529572037169917281779175818601414181211781493139916091132986838136714021325108513561222110211511136993665652679652496431530508384405480399426350187396295
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues21.017.312.428.455.348.147.149.448.653.340.152.735.147.742.352.336.835.129.246.348.448.638.248.847.243.243.645.241.031.333.237.237.835.130.438.335.829.830.536.733.035.428.815.932.726.6

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxExpenseBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-409.144132404462922762112484224693692633221566383269239190337353356257330292281268274268178190186159651361311218210412795117787510275
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-14.71.60.57.112.18.37.55.96.912.113.310.87.910.347.412.58.88.56.611.412.213.19.111.911.311.010.210.911.18.49.710.29.24.69.69.58.56.47.99.77.99.86.56.48.46.8

us-gaap:IncomeTaxExpenseBenefit us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value3.02.30.00.1-0.1-0.1-0.3-0.1-0.1-0.10.00.00.10.10.10.00.0
Percentage of IncomeTaxExpenseBenefit-0.75.20.00.0-0.0-0.0-0.1-0.0-0.0-0.00.00.00.00.00.00.00.0
Percentage of Revenues0.10.10.00.0-0.0-0.0-0.0-0.0-0.0-0.00.00.00.00.00.00.00.0
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossNetCashFlowHedgeParent9.8-10.00.0-1.1-0.4-0.40.0-0.3-0.3-0.70.00.01.00.30.00.00.0

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Income
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
Value0.10.1-0.90.0-0.83.4-0.6-0.1-0.1-0.10.20.00.01.66.20.30.00.30.10.00.20.00.10.50.10.00.10.0-3.60.0-3.9-0.10.0-1.4-0.90.10.3
Percentage of IncomeTaxExpenseBenefit-0.00.2-6.80.0-0.21.2-0.2-0.0-0.0-0.00.00.00.00.50.40.10.00.10.10.00.10.00.00.20.00.00.00.0-1.30.0-2.0-0.10.0-2.1-0.70.10.2
Percentage of Revenues0.00.0-0.00.0-0.00.1-0.0-0.0-0.0-0.00.00.00.00.10.20.00.00.00.00.00.00.00.00.00.00.00.00.0-0.10.0-0.2-0.00.0-0.1-0.10.00.0
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:IncomeTaxExpenseBenefit us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

biib:SamsungBiosimilarAgreement


Income
Period End2021-06-30
Value31
Percentage of IncomeTaxExpenseBenefit-7.6
Percentage of Revenues1.1
Percentage of Revenues biib:SamsungBiosimilarAgreement0.0

Interest Expense

us-gaap:InterestExpense

us-gaap:InterestExpense


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value5664565666444645474749495150626163636466656367155.86.77.47.47.17.66.46.67.311138.77.07.47.57.98.49.29.59.39.08.3
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues2.02.42.01.71.81.31.31.31.31.41.41.41.51.61.92.02.12.32.32.22.32.32.40.60.20.30.30.30.30.40.30.40.40.80.90.60.50.60.60.60.70.80.80.80.70.7

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value44841035770115421399143915451494140894614448661172-297.4122686274764910321049970831965927822883856714479457487490426292398386302300351288294240254293217305277142244
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues16.215.212.520.841.939.639.242.941.340.426.842.025.837.5-9.039.828.026.622.634.936.335.629.334.835.832.233.534.129.522.523.326.728.530.220.628.827.223.422.626.923.824.519.721.624.219.627.124.813.123.5

us-gaap:NetIncomeLoss us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value-27.6-21.4-17.7-6.62714403731169.8-8.7-10.7-37.4-28.9-18.8-2.86.34.7-5.3-4.78.753424034132.70.7-4.20.2-7.2-0.1
Percentage of NetIncomeLoss-6.2-5.2-4.9-0.91.81.12.82.42.11.21.0-0.6-1.2-3.29.7-1.5-0.30.80.7-0.5-0.40.96.44.44.34.21.50.30.1-0.90.0-1.5-0.0
Percentage of Revenues-1.0-0.8-0.6-0.20.80.41.11.00.90.50.3-0.3-0.3-1.2-0.9-0.6-0.10.20.2-0.2-0.20.31.91.51.51.40.50.10.0-0.20.0-0.4-0.0
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value577-5.6-0.32.464-6.50.00.00.00.0-1.9-1.548-1.71310.00.0-0.1-1.3-2.7-1.4-1.7-2.85353-2.451-2.367-0.879-0.7388.626-0.2280.00.00.00.00.00.00.295-0.295-0.0281.836161431-141.91.22.60.41.92.02.6
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues20.8-0.2-0.00.11.7-0.20.00.00.00.0-0.1-0.01.4-0.14.00.00.0-0.0-0.0-0.1-0.0-0.1-0.11.9-0.1-0.1-0.0-0.00.4-0.00.00.00.00.00.00.00.0-0.0-0.00.11.31.22.6-12.10.10.20.00.20.20.3

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense

us-gaap:NonoperatingIncomeExpense


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-09-302014-06-30
Value96-506.9683-128.663-120.5-49.3-27.3-197.4357-28.6115-34.5-41.0-66.0-43.6-68.2-37.6-48.0-58.1-58.5-52.8-82.412-15.413-10.889-15.0-16.294.861
Percentage of NonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues3.5-18.824.0-3.81.7-3.4-1.3-0.8-5.510.2-0.83.3-1.0-1.3-2.0-1.4-2.2-1.3-1.7-2.0-2.0-1.9-2.9-0.6-0.4-0.6-0.60.2

us-gaap:NonoperatingIncomeExpense us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-0.10.20.10.00.10.10.10.10.00.10.10.10.00.10.10.10.0
Percentage of NonoperatingIncomeExpense-0.1-0.00.0-0.00.2-0.1-0.2-0.4-0.00.0-0.30.1-0.0-0.2-0.2-0.2-0.0
Percentage of Revenues-0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossNetCashFlowHedgeParent-0.3-0.90.0-0.00.40.40.00.30.00.70.01.20.00.30.00.50.0

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-30
Value-0.4-0.54.2000000000000010.13.9-16.42.90.60.70.3-0.8-0.10.0-7.6-17.8-0.9-0.1-0.70.0-0.60.0-1.3-0.2-0.1-0.110
Percentage of NonoperatingIncomeExpense-0.40.10.6-0.16.213.6-5.9-2.2-0.40.12.8-0.1-0.018.527.02.10.11.9-0.01.0-0.08.41.80.70.6207.8
Percentage of Revenues-0.0-0.00.10.00.1-0.50.10.00.00.0-0.0-0.00.0-0.2-0.5-0.0-0.0-0.00.0-0.00.0-0.0-0.0-0.0-0.00.4
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest


Nonoperating
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.10.30.80.90.90.42.22.22.21.50.00.00.0
Percentage of NonoperatingIncomeExpense0.10.0-0.61.4-0.7-0.8-8.1-1.10.6-5.20.0-0.0-0.0
Percentage of Revenues0.00.00.00.00.00.00.10.10.10.00.00.00.0
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.0

Operating Expenses

us-gaap:OperatingExpenses us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:OperatingExpenses

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-400000.0400000.04700000.0-1500000.00100000.01300000.0800000.0700000.0500000.0-400000.0300000.0400000.01300000.0-100000.0500000.0300000.0
Percentage of OperatingExpenses100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-0.00.00.2-0.00.00.00.00.00.00.0-0.00.00.00.0-0.00.00.0
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossNetCashFlowHedgeParent-1.3-1.70.016.50.00.40.02.32.33.40.03.63.84.00.02.710.0

Operating Income Loss

us-gaap:OperatingIncomeLoss

us-gaap:OperatingIncomeLoss


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value485973-330.6108619741819177718061955150214431697121315341465165312001024886142514601378116813711233111711591152988671657684662510445535505369409488410416355194395303
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues17.536.2-11.632.253.651.548.450.254.143.140.949.436.149.044.353.739.036.430.948.250.550.641.149.447.643.843.945.940.831.533.537.538.436.131.438.635.628.630.837.334.034.629.116.532.627.4

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

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value15-48.5895016-63.95279-10.3-17.8-29.08.5-92.04412438220-75.8-14.4-58.09.6-35.078-23.50463-100.853-37.972-60.254-8.047-2.94419338.056-24.4192425-51.22625-50.113-50.50522
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.6-1.83.11.50.5-1.81.42.2-0.3-0.5-0.80.2-2.71.40.41.42.70.7-2.6-0.5-2.00.4-1.2-0.82.4-3.9-1.4-2.4-0.3-0.11.01.80.5-1.71.71.8-3.61.9-3.8-3.91.8

Other Comprehensive Income Loss Net Of Tax

us-gaap:OtherComprehensiveIncomeLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value2.4125-73.4-45.4-30.6-13.5-42.9160-33.5207.51342138.09.4-13.6-5.3172-18.1-23.5-35.3262-56.391-30.487-11.0541-11.309-4.3225.3891.572512-12.67-4.189-0.56-32.8478.891-34.084-18.94829
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.14.7-2.6-1.3-0.8-0.4-1.24.5-0.90.60.20.41.30.40.20.3-0.4-0.26.0-0.6-0.8-1.39.2-2.0-1.2-0.41.6-0.5-0.20.30.11.40.7-0.9-0.3-0.0-2.30.7-2.6-1.42.5

us-gaap:OtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value0.42.0-0.50.10.80.80.10.6-0.20.9-0.50.0-0.60.10.40.70.2-10.80.52.81.3-13.30.7-0.20.8-1.10.91.11.2
Percentage of OtherComprehensiveIncomeLossNetOfTax16.71.61.1-0.3-5.90.5-0.32.9-1.52.1-3.80.04.4-1.9-2.2-3.0-0.6-4.1-0.9-9.2-11.8-31.7-6.24.614.8-70.13.58.6-9.5
Percentage of Revenues0.00.1-0.00.00.00.00.00.0-0.00.0-0.00.0-0.00.00.00.00.0-0.40.00.10.1-0.50.0-0.00.0-0.10.00.10.1
Percentage of Revenues us-gaap:AccumulatedDefinedBenefitPlansAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-11.0149-83.7-51.23359-37.9165.2132-29.0-35.5
Percentage of OtherComprehensiveIncomeLossNetOfTax-458.3119.3184.4167.3-250.436.8113.182.039.1313.9-223.1-377.7
Percentage of Revenues-0.45.6-2.5-1.41.01.6-1.00.50.24.0-0.9-1.2
Percentage of Revenues us-gaap:AccumulatedGainLossNetCashFlowHedgeParent0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value-0.5-0.80.18.7-7.80.13.36.9-0.20.6-2.21.07.2-1.6-5.44.52.50.8-2.3-0.21.3-0.90.1-6.91.7-9.86.26.1-1.1
Percentage of OtherComprehensiveIncomeLossNetOfTax-20.8-0.6-0.2-28.457.80.1-9.933.5-1.51.4-16.910.6-52.930.229.8-19.1-7.10.34.10.7-11.8-2.1-0.9159.631.5-624.224.047.58.7
Percentage of Revenues-0.0-0.00.00.2-0.20.00.10.2-0.00.0-0.10.00.2-0.1-0.20.20.10.0-0.1-0.00.1-0.00.0-0.30.1-0.50.30.4-0.1
Percentage of Revenues us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value2.5124-73.5-44.5-31.7-14.1-42.9160-33.1
Percentage of OtherComprehensiveIncomeLossNetOfTax104.299.4100.198.0103.6104.4100.0100.098.8
Percentage of Revenues0.14.6-2.6-1.3-0.9-0.4-1.24.5-0.9
Percentage of Revenues us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-2.322-11.3-6.2232111143.50.00.00.0
Percentage of OtherComprehensiveIncomeLossNetOfTax-95.817.924.920.3-170.413.2-34.968.046.70.00.00.0
Percentage of Revenues-0.10.8-0.3-0.20.70.60.30.40.10.00.00.0
Percentage of Revenues us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedTranslationAdjustment


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value15-48.55016-63.979-10.3-17.88.5-92.044438220-14.4-58.09.6-35.1-23.563-100.9-38.0-60.2-8.1-2.919338.0-24.4
Percentage of OtherComprehensiveIncomeLossNetOfTax662.5-38.7-112.1-55.2473.349.430.7-86.463.9-217.5343.8467.0-608.8-377.479.6246.8-27.2-13.441.7-207.0913.1-90.5532.3187.4-53.81267.5130.162.3192.6
Percentage of Revenues0.6-1.81.50.5-1.82.2-0.3-0.50.2-2.71.41.42.70.7-0.5-2.00.4-1.2-0.82.4-3.9-1.4-2.4-0.3-0.11.01.80.5-1.7
Percentage of Revenues us-gaap:AccumulatedTranslationAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-0.10.70.1-0.91.10.60.00.0-0.40.0-0.10.0-0.50.2
Percentage of OtherComprehensiveIncomeLossNetOfTax-4.20.6-0.12.0-3.6-4.4-0.00.01.20.0-1.30.0-1.21.5
Percentage of Revenues-0.00.00.0-0.00.00.00.00.0-0.00.0-0.00.0-0.00.0
Percentage of Revenues us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value2.5124-73.5-44.5-31.7-14.1-42.9160-33.1
Percentage of OtherComprehensiveIncomeLossNetOfTax104.299.4100.198.0103.6104.4100.0100.098.8
Percentage of Revenues0.14.6-2.6-1.3-0.9-0.4-1.24.5-0.9
Percentage of Revenues us-gaap:Parent0.00.00.00.00.00.00.00.00.0

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:OtherNonoperatingIncomeExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value-3.00.12.50.74.2-4.4-36.0-3.7-7.1-0.2-1.7-3.2-3.8-1.8-4.9-5.1-5.82.7-203.1-4.4-5.5-4.4-116.6-2.0-8.2-14.986-8.751-16.294.861-5.601-5.405-4.64-10.428-14.457-14.29-4.5482.9515-3.973-7.727-11.7289.951-4.7-6.91.0-8.46.49.4146.8
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-0.10.00.10.00.1-0.1-1.0-0.1-0.2-0.0-0.0-0.1-0.1-0.1-0.1-0.2-0.20.1-7.1-0.1-0.2-0.2-4.1-0.1-0.3-0.6-0.3-0.60.2-0.3-0.3-0.3-0.6-1.0-1.0-0.30.21.2-0.3-0.6-1.00.8-0.4-0.60.1-0.80.60.81.30.7

Profit Loss

us-gaap:ProfitLoss

us-gaap:ProfitLoss


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value102540435770316061392143915451494140894414429151171-166.31226862747647103010489698281019924820882856723479457487490426292398387302300353304308271112294220306279144246
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues37.015.012.520.843.639.439.242.941.340.426.842.027.337.4-5.039.828.026.622.634.936.235.529.236.735.732.133.434.129.922.523.326.728.530.220.628.827.223.422.627.025.225.722.39.524.319.827.225.013.323.8

us-gaap:ProfitLoss us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312011-12-312011-09-302011-06-302010-12-312010-09-302010-06-30
Value577-5.6-0.32.464-6.5-0.0421.91631-141.91.2
Percentage of ProfitLoss56.3-1.4-0.10.34.0-0.5-0.00.55.311.6-126.50.4
Percentage of Revenues20.8-0.2-0.00.11.7-0.2-0.00.11.32.6-12.10.1
Percentage of Revenues us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value44841035770115421399143915451494
Percentage of ProfitLoss43.7101.4100.199.796.0100.5100.0100.0100.0
Percentage of Revenues16.215.212.520.841.939.639.242.941.3
Percentage of Revenues us-gaap:Parent0.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value44841035770115421399143915451494
Percentage of ProfitLoss43.7101.4100.199.796.0100.5100.0100.0100.0
Percentage of Revenues16.215.212.520.841.939.639.242.941.3
Percentage of Revenues us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.0

Realized Investment Gains Losses

us-gaap:RealizedInvestmentGainsLosses

us-gaap:RealizedInvestmentGainsLosses


Realized
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value153-436.664-82.1106-77.3-148.9-4.1-173.43761415.3-14.4-4.0-13.4
Percentage of RealizedInvestmentGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues5.5-16.22.3-2.42.9-2.2-4.1-0.1-4.810.84.10.2-0.5-0.1-0.4

Research And Development Expense

us-gaap:ResearchAndDevelopmentExpense us-gaap:TypeOfArrangement

us-gaap:ResearchAndDevelopmentExpense

biib:DenaliTherapeuticsInc


Research
Period End2021-06-302021-03-312020-09-30
Value0.04141
Percentage of ResearchAndDevelopmentExpense0.0100.0100.0
Percentage of Revenues0.01.50.0
Percentage of Revenues biib:DenaliTherapeuticsInc0.00.00.0

biib:SageTherapeuticsInc


Research
Period End2020-11-30
Value209
Percentage of ResearchAndDevelopmentExpense0.0
Percentage of Revenues0.0
Percentage of Revenues biib:SageTherapeuticsInc0.0

Research And Development Expense Excluding Acquired In Process Cost

us-gaap:ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost

us-gaap:ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost


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
Value58551417261140647476691540484563611507981496587446796423533529473437541519490460500417447528422410327284345304329
Percentage of ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues21.119.160.533.817.613.518.815.013.416.217.314.829.215.917.814.525.915.118.617.916.316.019.118.718.918.018.916.618.524.821.522.419.020.124.322.023.2

us-gaap:ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost us-gaap:TypeOfArrangement

biib:Otherresearchanddiscovery


Research
Period End2021-06-302020-06-30
Value779.6
Percentage of ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost13.21.5
Percentage of Revenues2.80.3
Percentage of Revenues biib:Otherresearchanddiscovery0.00.0

Revenues

us-gaap:Revenues

us-gaap:Revenues


Revenues
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value27752694285233763681353436713600361634893526343933563131330730773078281028722955289427262839277725912554264025112421212919651827172314151417138514201292132613091208120312191175121211081127112010931036
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Revenues us-gaap:MajorCustomers, us-gaap:ProductOrService

biib:ContractManufacturingCustomer, biib:Othercorporaterevenues


Revenuesus-gaap:
Period End2020-09-302020-06-30
Value333329
Percentage of Revenues9.98.9
Percentage of Revenues9.98.9
Percentage of Revenues biib:ContractManufacturingCustomer biib:Othercorporaterevenues100.0100.0

us-gaap:Revenues us-gaap:MajorCustomers, us-gaap:TypeOfArrangement

biib:SamsungBiosimilarAgreement, us-gaap:CollaborativeArrangement


Revenuesus-gaap:
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value200.00.53.716125224154814178.69.012
Percentage of Revenues0.70.00.00.10.40.41.40.70.41.40.40.60.30.30.4
Percentage of Revenues0.70.00.00.10.40.41.40.70.41.40.40.60.30.30.4
Percentage of Revenues biib:SamsungBiosimilarAgreement us-gaap:CollaborativeArrangement100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:ZINBRYTA, us-gaap:CollaborativeArrangement


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value5.53.95.44.50.21252-0.4
Percentage of Revenues0.20.10.20.10.00.41.4-0.0
Percentage of Revenues0.20.10.20.10.00.41.4-0.0
Percentage of Revenues biib:ZINBRYTA us-gaap:CollaborativeArrangement100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Revenues us-gaap:ProductOrService

biib:ADUHELM


Revenuesus-gaap:
Period End2021-06-30
Value1.6
Percentage of Revenues0.1
Percentage of Revenues0.1
Percentage of Revenues biib:ADUHELM100.0

biib:BENEPALI


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value121121117124106133126115120124125123115120117998865
Percentage of Revenues4.44.54.13.72.93.83.43.23.33.63.63.63.43.93.63.22.92.3
Percentage of Revenues4.44.54.13.72.93.83.43.23.33.63.63.63.43.93.63.22.92.3
Percentage of Revenues biib:BENEPALI100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Biosimilars


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value202205197207171218195183184174156134126127
Percentage of Revenues7.37.66.96.24.76.25.35.15.15.04.43.93.84.1
Percentage of Revenues7.37.66.96.24.76.25.35.15.15.04.43.93.84.1
Percentage of Revenues biib:Biosimilars100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:FAMPYRA


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value262625262328252424222222232424242220
Percentage of Revenues0.91.00.90.80.60.80.70.70.70.70.60.70.70.80.70.80.70.7
Percentage of Revenues0.91.00.90.80.60.80.70.70.70.70.60.70.70.80.70.80.70.7
Percentage of Revenues biib:FAMPYRA100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:FLIXABI


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value252526272023181816141411116.64.32.21.90.6
Percentage of Revenues0.90.90.90.80.60.70.50.50.50.40.40.30.30.20.10.10.10.0
Percentage of Revenues0.90.90.90.80.60.70.50.50.50.40.40.30.30.20.10.10.10.0
Percentage of Revenues biib:FLIXABI100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:FUMADERM


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value3.12.83.03.12.83.33.63.83.74.15.04.85.57.08.910109.7
Percentage of Revenues0.10.10.10.10.10.10.10.10.10.10.10.10.20.20.30.30.30.3
Percentage of Revenues0.10.10.10.10.10.10.10.10.10.10.10.10.20.20.30.30.30.3
Percentage of Revenues biib:FUMADERM100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Fumarate


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value57855264696711901100116611221150
Percentage of Revenues20.820.522.728.732.331.131.831.231.8
Percentage of Revenues20.820.522.728.732.331.131.831.231.8
Percentage of Revenues biib:Fumarate100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:IMRALDI


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value55575356446151494735160.00.00.0
Percentage of Revenues2.02.11.91.71.21.71.41.41.31.00.50.00.00.0
Percentage of Revenues2.02.11.91.71.21.71.41.41.31.00.50.00.00.0
Percentage of Revenues biib:IMRALDI100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

biib:Interferon


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value400400456474481466516530554500597590625550644662690648
Percentage of Revenues14.414.916.014.013.113.214.114.715.314.416.917.218.617.619.521.522.423.1
Percentage of Revenues14.414.916.014.013.113.214.114.715.314.416.917.218.617.619.521.522.423.1
Percentage of Revenues biib:Interferon100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:MSProductRevenues


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value15291483160319842126211721822160220419832194217222022025
Percentage of Revenues55.155.156.258.857.859.959.460.060.956.862.263.265.664.7
Percentage of Revenues55.155.156.258.857.859.959.460.060.956.862.263.265.664.7
Percentage of Revenues biib:MSProductRevenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Othercorporaterevenues


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value8783119110395941229310526414791791401433020
Percentage of Revenues3.13.14.23.310.72.73.32.62.97.64.22.72.44.54.41.00.7
Percentage of Revenues3.13.14.23.310.72.73.32.62.97.64.22.72.44.54.41.00.7
Percentage of Revenues biib:Othercorporaterevenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Revenuesfromanticd20therapeuticprograms


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value440389419560478520600595576517534511490443415406397340
Percentage of Revenues15.914.414.716.613.014.716.416.515.914.815.214.914.614.212.513.212.912.1
Percentage of Revenues15.914.414.716.613.014.716.416.515.914.815.214.914.614.212.513.212.912.1
Percentage of Revenues biib:Revenuesfromanticd20therapeuticprograms100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:SPINRAZA


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value49952049849449456554354748851846946742236336227020247
Percentage of Revenues18.019.317.514.613.416.014.815.213.514.913.313.612.611.611.08.86.61.7
Percentage of Revenues18.019.317.514.613.416.014.815.213.514.913.313.612.611.611.08.86.61.7
Percentage of Revenues biib:SPINRAZA100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:TysabriProduct


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value524503475516432522472483475460464470467462462469496545
Percentage of Revenues18.918.716.715.311.714.812.913.413.113.213.213.713.914.814.015.316.119.4
Percentage of Revenues18.918.716.715.311.714.812.913.413.113.213.213.713.914.814.015.316.119.4
Percentage of Revenues biib:TysabriProduct100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Product


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value223622112301269027952904292428942880268028252780275725232712262226392380
Percentage of Revenues80.682.180.779.775.982.279.780.479.676.880.180.882.280.682.085.285.784.7
Percentage of Revenues80.682.180.779.775.982.279.780.479.676.880.180.882.280.682.085.285.784.7
Percentage of Revenues us-gaap:Product100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductAndServiceOther


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value9993132125407109145109160292165147108164179484190
Percentage of Revenues3.63.54.63.711.13.14.03.04.48.44.74.33.25.35.41.61.43.2
Percentage of Revenues3.63.54.63.711.13.14.03.04.48.44.74.33.25.35.41.61.43.2
Percentage of Revenues us-gaap:ProductAndServiceOther100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Royalty


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value6.46.25.1107.1117.13.32.73.92.97.91710201111
Percentage of Revenues0.20.20.20.30.20.30.20.10.10.10.10.20.50.30.60.40.4
Percentage of Revenues0.20.20.20.30.20.30.20.10.10.10.10.20.50.30.60.40.4
Percentage of Revenues us-gaap:Royalty100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

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

biib:ADUHELM, country:US


Revenuesus-gaap:
Period End2021-06-30
Value1.6
Percentage of Revenues0.1
Percentage of Revenues0.1
Percentage of Revenues biib:ADUHELM country:US100.0

biib:BENEPALI, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value121121117124106133126115120124125123115120
Percentage of Revenues4.44.54.13.72.93.83.43.23.33.63.63.63.43.9
Percentage of Revenues4.44.54.13.72.93.83.43.23.33.63.63.63.43.9
Percentage of Revenues biib:BENEPALI us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Biosimilars, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value202205197207171218195183184174156134126127
Percentage of Revenues7.37.66.96.24.76.25.35.15.15.04.43.93.84.1
Percentage of Revenues7.37.66.96.24.76.25.35.15.15.04.43.93.84.1
Percentage of Revenues biib:Biosimilars us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:FAMPYRA, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2626252623282524242222222324
Percentage of Revenues0.91.00.90.80.60.80.70.70.70.70.60.70.70.8
Percentage of Revenues0.91.00.90.80.60.80.70.70.70.70.60.70.70.8
Percentage of Revenues biib:FAMPYRA us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:FLIXABI, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value252526272023181816141411116.6
Percentage of Revenues0.90.90.90.80.60.70.50.50.50.40.40.30.30.2
Percentage of Revenues0.90.90.90.80.60.70.50.50.50.40.40.30.30.2
Percentage of Revenues biib:FLIXABI us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:FUMADERM, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value3.12.83.03.12.83.33.63.83.74.15.04.85.57.0
Percentage of Revenues0.10.10.10.10.10.10.10.10.10.10.10.10.20.2
Percentage of Revenues0.10.10.10.10.10.10.10.10.10.10.10.10.20.2
Percentage of Revenues biib:FUMADERM us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Fumarate, country:US


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value269236358684921777882842869
Percentage of Revenues9.78.812.620.325.022.024.023.424.0
Percentage of Revenues9.78.812.620.325.022.024.023.424.0
Percentage of Revenues biib:Fumarate country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Fumarate, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value309316288283268323284280280
Percentage of Revenues11.111.810.18.47.39.17.77.87.8
Percentage of Revenues11.111.810.18.47.39.17.77.87.8
Percentage of Revenues biib:Fumarate us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:IMRALDI, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value55575356446151494735160.00.00.0
Percentage of Revenues2.02.11.91.71.21.71.41.41.31.00.50.00.00.0
Percentage of Revenues2.02.11.91.71.21.71.41.41.31.00.50.00.00.0
Percentage of Revenues biib:IMRALDI us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

biib:Interferon, country:US


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value257241308327345292359360379327430421444371449473501464
Percentage of Revenues9.39.010.89.79.48.39.810.010.59.412.212.313.211.913.615.416.316.5
Percentage of Revenues9.39.010.89.79.48.39.810.010.59.412.212.313.211.913.615.416.316.5
Percentage of Revenues biib:Interferon country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Interferon, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value143158148146135173157169174173166168180178
Percentage of Revenues5.25.95.24.33.74.94.34.74.85.04.74.95.45.7
Percentage of Revenues5.25.95.24.33.74.94.34.74.85.04.74.95.45.7
Percentage of Revenues biib:Interferon us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:MSProductRevenues, country:US


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value82675193713151511134715111465151312901544151615361350
Percentage of Revenues29.827.932.939.041.138.141.240.741.937.043.844.145.843.1
Percentage of Revenues29.827.932.939.041.138.141.240.741.937.043.844.145.843.1
Percentage of Revenues biib:MSProductRevenues country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:MSProductRevenues, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value702732665669615769670694690693650656666675
Percentage of Revenues25.327.223.319.816.721.818.319.319.119.918.519.119.921.6
Percentage of Revenues25.327.223.319.816.721.818.319.319.119.918.519.119.921.6
Percentage of Revenues biib:MSProductRevenues us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:SPINRAZA, country:US


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value14914815918221023524223623022323622320518821819719446
Percentage of Revenues5.45.55.65.45.76.76.66.66.46.46.76.56.16.06.66.46.31.7
Percentage of Revenues5.45.55.65.45.76.76.66.66.46.46.76.56.16.06.66.46.31.7
Percentage of Revenues biib:SPINRAZA country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:SPINRAZA, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value350371338311284329300310257295233243216175
Percentage of Revenues12.613.811.99.27.79.38.28.67.18.56.67.16.55.6
Percentage of Revenues12.613.811.99.27.79.38.28.67.18.56.67.16.55.6
Percentage of Revenues biib:SPINRAZA us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:TysabriProduct, country:US


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value299273270304244277269263264245256253265249252266289305
Percentage of Revenues10.810.19.59.06.67.97.37.37.37.07.37.47.98.07.68.79.410.9
Percentage of Revenues10.810.19.59.06.67.97.37.37.37.07.37.47.98.07.68.79.410.9
Percentage of Revenues biib:TysabriProduct country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:TysabriProduct, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value224230204212187244203220211215207217201212
Percentage of Revenues8.18.57.26.35.16.95.56.15.86.25.96.36.06.8
Percentage of Revenues8.18.57.26.35.16.95.56.15.86.25.96.36.06.8
Percentage of Revenues biib:TysabriProduct us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Product, country:US


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value977899109714981721158317541702174415131780174017411538175117741860
Percentage of Revenues35.233.438.544.446.844.847.847.348.243.450.550.651.949.153.057.660.5
Percentage of Revenues35.233.438.544.446.844.847.847.348.243.450.550.651.949.153.057.660.5
Percentage of Revenues us-gaap:Product country:US100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Product, us-gaap:NonUs


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1258131112041192107413211170119211351166104510391015985
Percentage of Revenues45.448.742.235.329.237.431.933.131.433.429.630.230.331.5
Percentage of Revenues45.448.742.235.329.237.431.933.131.433.429.630.230.331.5
Percentage of Revenues us-gaap:Product us-gaap:NonUs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value30-23.1-23.3-9.1232738352914-9.28.4103217183.0
Percentage of Revenues1.1-0.9-0.8-0.30.60.81.11.00.80.4-0.30.20.31.10.50.60.1
Percentage of Revenues1.1-0.9-0.8-0.30.60.81.11.00.80.4-0.30.20.31.10.50.60.1
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossNetCashFlowHedgeParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Revenues us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:TypeOfArrangement

biib:SamsungBiosimilarAgreement, us-gaap:CollaborativeArrangement


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value5.44.53.712522415481417198.812
Percentage of Revenues0.20.10.10.41.40.70.41.40.40.60.60.30.4
Percentage of Revenues0.20.10.10.41.40.70.41.40.40.60.60.30.4
Percentage of Revenues biib:SamsungBiosimilarAgreement us-gaap:CollaborativeArrangement100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Selling General And Administrative Expense

us-gaap:SellingGeneralAndAdministrativeExpense

us-gaap:SellingGeneralAndAdministrativeExpense


Selling
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value637595806573555570664554587567591497516501572433430499495462492497583477491560573570576511522405431352375299301300283261266244276244262248
Percentage of SellingGeneralAndAdministrativeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues23.022.128.317.015.116.118.115.416.216.316.814.515.416.017.314.114.017.817.315.717.018.220.517.219.021.921.722.723.824.026.622.225.024.926.521.621.223.221.420.022.020.322.720.821.622.4

Assets

us-gaap:Assets

us-gaap:Assets


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value2447023854246182493425511261192723427484262872644525288254922395226090236522307321759211952287622104215142067419504207281675915219143161370412917122301186311250108411016410130963091629113904988028621829380928551
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities

us-gaap:Liabilities


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value132551319113932141891422213582138951349213338126231225711732116991205211054102241018597281074899901011110346101291016141863549350232733352308932423124293928253166296828912805262225682565261926432289
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets54.255.356.656.955.752.051.049.150.747.748.546.048.846.246.744.346.845.947.045.247.050.051.949.025.023.324.523.926.025.327.327.827.127.831.330.831.630.829.029.229.831.632.726.8

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:LiabilitiesAndStockholdersEquity


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value2447023854246182493425511261192723427484262872644525288254922395226090236522307321759211952287622104215142067419504207281675915219143161370412917122301186311250108411016410130963091629113904988028621829380928551
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value10751106821070010758113081254613343139951295213829130391376612260140531261212860115851147912140121171140310326937210572125721166610809104279561913686208125790173396961665962686305642562295977560453966221
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets43.944.843.543.144.348.049.050.949.352.351.654.051.253.953.355.753.254.253.154.853.049.948.151.075.076.775.576.174.074.772.772.272.972.268.769.168.469.271.070.869.367.666.772.8

Assets Current

us-gaap:AssetsCurrent

us-gaap:AssetsCurrent


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value718367196887784384938007838184487909894276408719743210195787375687108685987328091744772016700927056185258467243723925352531842643252353283244305528682677297528372688262825402480
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets29.428.228.031.533.330.730.830.730.133.830.234.231.039.133.332.832.732.438.236.634.634.834.444.733.534.632.631.930.428.826.823.523.352.432.031.731.329.432.932.231.231.731.429.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value174212171331222423842591291323431723224312241573
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.15.15.48.99.39.910.78.56.68.54.86.7

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent

us-gaap:AccountsReceivableNetCurrent


Accounts
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value168818541913202421332092188019331959208819582017195119391787156716301501144114671293139512271327131013891292109110021018824891861753686661683684584581666687605551
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.97.87.88.18.48.06.97.07.57.97.77.98.17.47.66.87.57.16.36.66.06.76.36.47.89.19.08.07.88.36.97.97.97.46.86.97.57.56.56.67.78.37.56.4

Inventory Net

us-gaap:InventoryNet

us-gaap:InventoryNet


Inventory
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value1254117110681027952858804751776770929916931890902100793692110011009996964893918865825804753715672659614570506447392362337326310308289
Percentage of InventoryNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.14.94.34.13.73.33.02.73.02.93.73.63.93.43.84.44.34.34.44.64.64.74.64.45.25.45.65.55.55.55.65.55.35.04.44.14.03.73.63.53.63.6

Other Assets Current

us-gaap:OtherAssetsCurrent

us-gaap:OtherAssetsCurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value7677868816836386836317439809656878488438959629671146123110939931027941836861750579447396346295226205173169136126149122144194201186215177
Percentage of OtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.13.33.62.72.52.62.32.73.73.72.73.33.53.44.14.25.35.84.84.54.84.64.34.24.53.83.12.92.72.41.91.81.61.71.31.31.61.31.62.22.32.22.72.1

Land

us-gaap:Land

us-gaap:Land


Land
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value119118144141137745659555451107111
Percentage of Land100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.50.40.60.60.60.40.40.50.50.60.61.31.3

Machinery And Equipment Gross

us-gaap:MachineryAndEquipmentGross

us-gaap:MachineryAndEquipmentGross


Machinery
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value102784412581207110510791011944882824570576534
Percentage of MachineryAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.23.15.05.14.85.57.18.08.78.66.37.16.2

Noncurrent Assets

us-gaap:NoncurrentAssets

us-gaap:NoncurrentAssets


Noncurrent
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value384436743601318225012187176517501742183818261805
Percentage of NoncurrentAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets15.613.514.213.510.911.212.314.817.220.322.621.1

us-gaap:NoncurrentAssets us-gaap:StatementGeographical

biib:SegmentGeographicalGroupsOfCountriesGroupOther


Noncurrent
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value10121.82.11.41.73.23.32.22.41.62.1
Percentage of NoncurrentAssets0.30.30.00.10.10.10.20.20.10.10.10.1
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets biib:SegmentGeographicalGroupsOfCountriesGroupOther0.00.00.00.00.00.00.00.00.00.00.00.0

biib:Solothurn


Noncurrent
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value2180202817481215545161
Percentage of NoncurrentAssets56.755.248.638.221.87.4
Percentage of Assets8.97.46.95.12.40.8
Percentage of Assets biib:Solothurn0.00.00.00.00.00.0

country:US


Noncurrent
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value1496149311521226127212961055984996101211001092
Percentage of NoncurrentAssets38.940.632.038.650.959.359.856.257.255.160.360.5
Percentage of Assets6.15.54.65.25.66.67.48.39.811.213.612.8
Percentage of Assets country:US0.00.00.00.00.00.00.00.00.00.00.00.0

srt:Asia


Noncurrent
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value166.23.95.27.0
Percentage of NoncurrentAssets0.40.20.10.20.3
Percentage of Assets0.10.00.00.00.0
Percentage of Assets srt:Asia0.00.00.00.00.0

srt:Europe


Noncurrent
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value23212162244219481221
Percentage of NoncurrentAssets60.458.967.861.248.8
Percentage of Assets9.47.99.78.25.3
Percentage of Assets srt:Europe0.00.00.00.00.0

Property Plant And Equipment Gross

us-gaap:PropertyPlantAndEquipmentGross

us-gaap:PropertyPlantAndEquipmentGross


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value5193483853984741394135172952286926832574235324082279
Percentage of PropertyPlantAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets21.117.821.320.017.218.020.624.226.526.726.029.826.7

us-gaap:PropertyPlantAndEquipmentGross biib:FacilityLocation

biib:Solothurn


Property
Period End2020-12-31
Value256
Percentage of PropertyPlantAndEquipmentGross4.9
Percentage of Assets1.0
Percentage of Assets biib:Solothurn0.0

biib:SolothurnSwitzerland


Property
Period End2021-06-302020-09-30
Value1300256
Percentage of PropertyPlantAndEquipmentGross0.00.0
Percentage of Assets5.31.0
Percentage of Assets biib:SolothurnSwitzerland0.00.0

Furniture And Fixtures Gross

us-gaap:FurnitureAndFixturesGross

us-gaap:FurnitureAndFixturesGross


Furniture
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value62586155607264604643375450
Percentage of FurnitureAndFixturesGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.30.20.20.20.30.40.40.50.50.40.40.70.6

Leasehold Improvements Gross

us-gaap:LeaseholdImprovementsGross

us-gaap:LeaseholdImprovementsGross


Leasehold
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value10499948012316615513910710510210073
Percentage of LeaseholdImprovementsGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.40.40.40.30.50.91.11.21.11.11.11.20.9

Construction In Progress Gross

us-gaap:ConstructionInProgressGross

us-gaap:ConstructionInProgressGross


Construction
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312016-03-312015-12-312014-12-312013-12-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value1950208417581276658158441168144212242553506506
Percentage of ConstructionInProgressGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.97.77.05.42.90.82.31.21.22.12.56.16.35.9

us-gaap:ConstructionInProgressGross biib:FacilityLocation

biib:Solothurn


Construction
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value180019001600120048199
Percentage of ConstructionInProgressGross92.391.291.094.073.122.4
Percentage of Assets7.37.06.35.12.10.5
Percentage of Assets biib:Solothurn0.00.00.00.00.00.0

biib:SolothurnSwitzerland


Construction
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-31
Value6181900180018001700170019001800180017001600160015001300120096879860948135024799
Percentage of ConstructionInProgressGross0.00.092.30.00.00.091.20.00.00.091.00.00.00.094.00.00.00.073.10.00.022.4
Percentage of Assets2.58.07.37.26.76.57.06.56.86.46.36.36.35.05.14.23.72.92.11.61.20.5
Percentage of Assets biib:SolothurnSwitzerland0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value188018271782173416871636159015551886184117971730167116311559158015111438143915281471139413301320127412171186124612101163111810741030983941-898.3854821782749771789767642
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.77.77.27.06.66.35.85.77.27.07.16.87.06.36.66.96.96.86.36.96.86.76.86.47.68.08.39.19.49.59.49.59.59.79.3-9.39.39.08.68.58.99.59.57.5

Amortization Of Intangible Assets

us-gaap:AmortizationOfIntangibleAssets

us-gaap:AmortizationOfIntangibleAssets


Amortization
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value58636171-148.22837068-112.028110710313910811744810499928896989295107122116143109998251505352455049555353535348
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:PropertyPlantAndEquipmentNet


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value34423438341133593330328132473138307730133601353834093334318229952827261025012387230122582187202718371739176517241756174417501806178717361742167616221617157115721712167316411637
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets14.114.413.913.513.112.611.911.411.711.414.213.914.212.813.513.013.012.310.910.810.710.911.29.811.011.412.312.613.614.314.816.116.517.117.217.417.717.717.417.919.920.220.319.1

Goodwill

us-gaap:Goodwill

us-gaap:Goodwill


Goodwill
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value576357635762575557515752575757465749563957065440517049074632412738703611366934193167291726632408215418491760154113641232123212101210121012011204119711931146114611461146114611381138
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets23.624.223.423.122.522.021.120.921.921.322.621.321.618.819.617.917.817.016.015.514.714.113.711.612.912.212.311.210.610.110.410.811.211.911.912.513.113.112.713.013.313.814.213.30.0

Indefinite Lived Intangible Assets Excluding Goodwill

us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill biib:Researchanddevelopmentasset, us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass

us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill

biib:BIIB111, us-gaap:InProcessResearchAndDevelopment


Indefinite
Period End2021-06-302021-03-31
Value15365
Percentage of IndefiniteLivedIntangibleAssetsExcludingGoodwill100.0100.0
Percentage of Assets0.11.5
Percentage of Assets biib:BIIB111 us-gaap:InProcessResearchAndDevelopment0.00.0

biib:BIIB112, us-gaap:InProcessResearchAndDevelopment


Indefinite
Period End2021-06-302021-03-31
Value28220
Percentage of IndefiniteLivedIntangibleAssetsExcludingGoodwill189.360.3
Percentage of Assets0.10.9
Percentage of Assets biib:BIIB112 us-gaap:InProcessResearchAndDevelopment0.00.0

biib:TGN, us-gaap:InProcessResearchAndDevelopment


Indefinite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312018-09-30
Value13613517716716016141
Percentage of IndefiniteLivedIntangibleAssetsExcludingGoodwill906.737.00.00.00.00.00.0
Percentage of Assets0.60.60.70.70.60.60.2
Percentage of Assets biib:TGN us-gaap:InProcessResearchAndDevelopment0.00.00.00.00.00.00.0

us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass

us-gaap:InProcessResearchAndDevelopment


Indefinite
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
Value1797207629439549569659541175480476480670696680680668653648679692718730735752726314314330330327327327330
Percentage of IndefiniteLivedIntangibleAssetsExcludingGoodwill1196.0197.30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets0.73.03.13.83.73.73.53.54.51.81.91.92.82.72.92.93.13.12.83.13.23.53.73.54.54.82.22.32.62.72.82.93.03.3
Percentage of Assets us-gaap:InProcessResearchAndDevelopment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Intangible Assets Net Excluding Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill


Intangible
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value23852988308433233383344635273392368130563120337936613794387940194051410338083869396740124085418142944353402841294249436444744580467815811631168117321783160816591678173117721871
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets9.712.512.513.313.313.213.012.314.011.612.313.315.314.516.417.418.619.416.617.518.419.420.920.225.628.628.130.132.935.737.740.743.215.616.117.518.919.617.818.819.520.921.921.9

us-gaap:IntangibleAssetsNetExcludingGoodwill biib:Researchanddevelopmentasset, us-gaap:FairValueByMeasurementFrequency

biib:BIIB111, us-gaap:FairValueMeasurementsNonrecurring


Intangible
Period End2020-12-31
Value365
Percentage of IntangibleAssetsNetExcludingGoodwill11.8
Percentage of Assets1.5
Percentage of Assets biib:BIIB111 us-gaap:FairValueMeasurementsNonrecurring0.0

us-gaap:IntangibleAssetsNetExcludingGoodwill biib:Researchanddevelopmentasset, us-gaap:FiniteLivedIntangibleAssetsByMajorClass

biib:BIIB111, us-gaap:InProcessResearchAndDevelopment


Intangible
Period End2020-12-312020-09-30
Value365480
Percentage of IntangibleAssetsNetExcludingGoodwill11.814.4
Percentage of Assets1.51.9
Percentage of Assets biib:BIIB111 us-gaap:InProcessResearchAndDevelopment0.00.0

Finite Lived Intangible Assets Net

us-gaap:FiniteLivedIntangibleAssetsNet

us-gaap:FiniteLivedIntangibleAssetsNet


Finite
Period End2020-12-312019-12-312018-12-312011-12-31
Value2257249725800.0
Percentage of FiniteLivedIntangibleAssetsNet100.0100.0100.00.0
Percentage of Assets9.29.210.20.0

us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass

biib:OutLicensedPatents


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value21412204225723162364242624970.80.90.91.01.73.45.57.7101316192328323743495561697785127134142149157164171179186196207227
Percentage of FiniteLivedIntangibleAssetsNet0.00.0100.00.00.00.0100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets8.89.29.29.39.39.39.20.00.00.00.00.00.00.00.00.00.10.10.10.10.10.20.20.20.30.40.40.50.60.71.11.21.31.51.51.71.92.02.12.22.42.8
Percentage of Assets biib:OutLicensedPatents0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Deferred Tax Assets Liabilities Net

us-gaap:DeferredTaxAssetsLiabilitiesNet

us-gaap:DeferredTaxAssetsLiabilitiesNet


Deferred
Period End2021-06-30
Value500
Percentage of DeferredTaxAssetsLiabilitiesNet100.0
Percentage of Assets2.0

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
Value4024144334344364224274224344470.0
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets1.61.71.81.71.71.61.61.51.71.70.0

us-gaap:OperatingLeaseRightOfUseAsset us-gaap:BalanceSheetLocation

biib:Operatingleaseassets


Operating
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value433427422434447
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0
Percentage of Assets1.81.61.51.71.7
Percentage of Assets biib:Operatingleaseassets0.00.00.00.00.0

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent

us-gaap:OtherAssetsNoncurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value252824232899183414831130125212381306189816901009902380102713001268118413351239115310941107892751640618565611639594636533306274271271368331237211228248230
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets10.310.211.87.45.84.34.64.55.07.26.74.03.81.54.35.65.85.65.85.65.45.35.74.34.54.24.34.14.75.25.05.74.93.02.72.83.04.03.72.72.52.83.12.7

Equity Securities Fv Ni

us-gaap:EquitySecuritiesFvNi

us-gaap:EquitySecuritiesFvNi


Equity
Period End2020-12-31
Value1974
Percentage of EquitySecuritiesFvNi100.0
Percentage of Assets8.0

us-gaap:EquitySecuritiesFvNi us-gaap:FinancialInstrument

biib:EquitySecuritiesCurrent


Equity
Period End2021-06-302021-03-312020-12-31
Value1593144286
Percentage of EquitySecuritiesFvNi0.00.04.4
Percentage of Assets6.56.00.4
Percentage of Assets biib:EquitySecuritiesCurrent0.00.00.0

biib:EquitySecuritiesNonCurrent


Equity
Period End2021-06-302021-03-312020-12-312019-12-31
Value159314421887337
Percentage of EquitySecuritiesFvNi0.00.095.60.0
Percentage of Assets6.56.07.71.2
Percentage of Assets biib:EquitySecuritiesNonCurrent0.00.00.00.0

Accounts Payable Current

us-gaap:AccountsPayableCurrent

us-gaap:AccountsPayableCurrent


Accounts
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value375430454398383389530382377378370342295345395298330316279274225271267251282236229233224212219166163165203157159173186159170159162118
Percentage of AccountsPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.51.81.81.61.51.51.91.41.41.41.51.31.21.31.71.31.51.51.21.21.01.31.41.21.71.61.61.71.71.71.91.51.51.62.01.61.71.92.11.82.01.92.01.4

Liabilities Current

us-gaap:LiabilitiesCurrent

us-gaap:LiabilitiesCurrent


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value334731653742380434474638486344323210314832953174315231523368344833792992341924992516277625772633255519462219194019161594175815181304128116571521143213379128859549781050714
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets13.713.315.215.313.517.817.916.112.211.913.012.513.212.114.214.915.514.114.911.311.713.413.212.715.312.815.514.214.813.014.813.512.012.616.415.815.614.710.110.111.111.813.08.4

Operating Lease Liability Current

us-gaap:OperatingLeaseLiabilityCurrent us-gaap:BalanceSheetLocation

us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:AccruedLiabilities


Operating
Period End2020-12-312019-12-31
Value8373
Percentage of OperatingLeaseLiabilityCurrent100.0100.0
Percentage of Assets0.30.3
Percentage of Assets us-gaap:AccruedLiabilities0.00.0

Other Accrued Liabilities Current

us-gaap:OtherAccruedLiabilitiesCurrent

us-gaap:OtherAccruedLiabilitiesCurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-31
Value7607007911274774662726677727708609640638653636606591475685566613582579549433403456276263285
Percentage of OtherAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.12.93.25.13.02.52.72.52.82.72.42.52.72.52.72.62.72.23.02.62.92.83.02.62.62.73.22.02.02.4

us-gaap:OtherAccruedLiabilitiesCurrent us-gaap:BalanceSheetLocation

us-gaap:OtherCurrentLiabilities


Other
Period End2020-12-312019-12-31
Value791798
Percentage of OtherAccruedLiabilitiesCurrent100.0109.8
Percentage of Assets3.22.9
Percentage of Assets us-gaap:OtherCurrentLiabilities0.00.0

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent

us-gaap:OtherLiabilitiesCurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value274125923145328624862437276524292318243528612578263325712901245524362044290320122072200320961918181213841819154414951216135512041056885979866762660677674641591665500
Percentage of OtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.210.912.813.29.79.310.28.88.89.211.310.111.09.912.310.611.29.612.79.19.69.710.89.310.89.112.711.311.69.911.410.79.78.79.79.08.37.27.57.77.47.18.25.9

us-gaap:OtherLiabilitiesCurrent us-gaap:BalanceSheetLocation

us-gaap:OtherCurrentLiabilities


Other
Period End2020-12-312019-12-31
Value31452765
Percentage of OtherLiabilitiesCurrent100.0100.0
Percentage of Assets12.810.2
Percentage of Assets us-gaap:OtherCurrentLiabilities0.00.0

Taxes Payable Current

us-gaap:TaxesPayableCurrent

us-gaap:TaxesPayableCurrent


Taxes
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value2301431421195763107112542723863254223231681215270231208212496208458457322168159192161179144812820445850454710938475
Percentage of TaxesPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.90.60.60.52.31.20.30.51.60.90.31.00.90.90.30.50.20.31.00.91.02.41.12.22.72.11.21.21.51.31.51.30.80.30.20.50.60.50.50.50.11.11.00.9

Long Term Debt

us-gaap:LongTermDebt

us-gaap:LongTermDebt


Long
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
Value726972677426742574234459445944585948594359365931592859295935593859545952651265296538653565216529576580582583586591592694726687
Percentage of LongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets29.730.530.229.829.117.116.416.222.622.523.523.324.822.725.125.727.428.128.529.530.431.633.431.53.43.84.14.34.54.85.06.26.76.8

us-gaap:LongTermDebt us-gaap:LongtermDebtType

us-gaap:SeniorNotes


Long
Period End2020-12-312019-12-31
Value74264459
Percentage of LongTermDebt100.0100.0
Percentage of Assets30.216.4
Percentage of Assets us-gaap:SeniorNotes0.00.0

Deferred Income Tax Liabilities Net

us-gaap:DeferredIncomeTaxLiabilitiesNet

us-gaap:DeferredIncomeTaxLiabilitiesNet


Deferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value91896610321123146127222810
Percentage of DeferredIncomeTaxLiabilitiesNet100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.84.14.24.55.710.410.3

Minority Interest

us-gaap:MinorityInterest

us-gaap:MinorityInterest


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-31
Value462-19.0-14.2-14.0-19.5-10.0-4.1-4.1-4.1-7.9-8.0-6.8-7.2-16.2-14.7-11.6-11.6-11.6-11.5-2.7-0.11.32.1-5.7830.4212.6875.033.1893.9274.3520.5960.5960.5960.5962.2722.3882.3882.6471.4884.44679705239404140
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.9-0.1-0.1-0.1-0.1-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.1-0.1-0.1-0.1-0.1-0.0-0.00.00.0-0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.90.80.70.00.00.00.5

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:OtherLiabilitiesNoncurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value135614111329142814751357134813701355135313891511145716401628716750688722862951916905861915892650658710702659608595674604539534517400384351356325254
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.55.95.45.75.85.25.05.05.25.15.55.96.16.36.93.13.53.23.23.94.44.44.64.25.55.94.54.85.55.75.65.45.56.66.05.65.85.74.44.44.14.34.03.0

Operating Lease Liability Noncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent


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
Value3633804024094144034124104234360.0
Percentage of OperatingLeaseLiabilityNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets1.51.61.61.61.61.51.51.51.61.60.0

us-gaap:OperatingLeaseLiabilityNoncurrent us-gaap:BalanceSheetLocation

biib:Longtermoperatingleaseliabilities


Operating
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value402412410423436
Percentage of OperatingLeaseLiabilityNoncurrent100.0100.0100.0100.0100.0
Percentage of Assets1.61.51.51.61.6
Percentage of Assets biib:Longtermoperatingleaseliabilities0.00.00.00.00.0

Lessee Operating Lease Liability Payments Due Year Two

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo


Lessee
Period End2020-12-31
Value93
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearTwo100.0
Percentage of Assets0.4

Lessee Operating Lease Liability Payments Due Year Three

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree


Lessee
Period End2020-12-31
Value82
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearThree100.0
Percentage of Assets0.3

Lessee Operating Lease Liability Payments Due Year Four

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour


Lessee
Period End2020-12-31
Value75
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFour100.0
Percentage of Assets0.3

Lessee Operating Lease Liability Payments Due Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive


Lessee
Period End2020-12-31
Value56
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive100.0
Percentage of Assets0.2

Lessee Operating Lease Liability Payments Due After Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive


Lessee
Period End2020-12-31
Value129
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive100.0
Percentage of Assets0.5

Operating Lease Liability

us-gaap:OperatingLeaseLiability

us-gaap:OperatingLeaseLiability


Operating
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value485486481495508
Percentage of OperatingLeaseLiability100.0100.0100.0100.0100.0
Percentage of Assets2.01.81.81.91.9

Lessee Operating Lease Liability Payments Due

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue


Lessee
Period End2020-12-31
Value533
Percentage of LesseeOperatingLeaseLiabilityPaymentsDue100.0
Percentage of Assets2.2

Lessee Operating Lease Liability Undiscounted Excess Amount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount


Lessee
Period End2020-12-31
Value47
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount100.0
Percentage of Assets0.2

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value10751106821070010758113081254613343139951295213829130391376612260140531261212860115851147912140121171140310326937210572125721166610809104279561913686208125790173396961665962686305642562295977560453966221
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets43.944.843.543.144.348.049.050.949.352.351.654.051.253.953.355.753.254.253.154.853.049.948.151.075.076.775.576.174.074.772.772.272.972.268.769.168.469.271.070.869.367.666.772.8

Stockholders Equity Including Portion Attributable To Noncontrolling Interest

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value1121410663106861074411289125361333913991129481382213031137591225314037125981284811573114671212812114114031032893741056612572116691081410430956591418620812579027339696366616270630864266233605656745449626158335554
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets45.844.743.443.144.348.049.050.949.352.351.554.051.253.853.355.753.254.153.054.853.050.048.151.075.076.775.576.174.074.772.772.272.972.268.769.268.469.271.070.870.268.467.373.20.00.0

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-171.8-174.3-299.0-225.5-181.0-149.3-135.2-92.3-252.9-219.8-240.4-248.3-261.6-303.931831922459-27.745-55.305-26.535-21.6150-11.10679
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-1.5-1.6-2.8-2.1-1.6-1.2-1.0-0.7-2.0-1.6-1.8-1.8-2.1-2.22.52.62.40.6-0.3-0.8-0.4-0.40.8-0.21.4
Percentage of Assets-0.7-0.7-1.2-0.9-0.7-0.6-0.5-0.3-1.0-0.8-1.0-1.0-1.1-1.21.31.41.10.4-0.2-0.5-0.3-0.30.60.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.1290.1280.1270.1280.1240.1440.1490.147
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NoncontrollingInterest


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value462-19.0-14.2-14.0-19.5-10.0-4.1-4.1-4.1-7.9-8.0-14.72.15.030.5962.2721.48852402719
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest4.1-0.2-0.1-0.1-0.2-0.1-0.0-0.0-0.0-0.1-0.1-0.10.00.00.00.00.01.00.60.50.4
Percentage of Assets1.9-0.1-0.1-0.1-0.1-0.0-0.0-0.0-0.0-0.0-0.0-0.10.00.00.00.00.00.70.50.00.0
Percentage of Assets us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-312010-12-312009-12-312008-12-312007-12-31
Value1075110682107001075811308125461334313995129521382913039126125396622158065534
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest95.9100.2100.1100.1100.2100.1100.0100.0100.0100.1100.1100.199.099.499.599.6
Percentage of Assets43.944.843.543.144.348.049.050.949.352.351.653.366.772.80.00.0
Percentage of Assets us-gaap:Parent0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value1390013833139761396114466156731645517065161821702616257169441549917334158101507112208928363494486310618721068270-352.169
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest123.9129.7130.8129.9128.1125.0123.4122.0125.0123.2124.8123.1126.5123.5125.5124.3130.285.973.664.448.334.417.14.6-6.3
Percentage of Assets56.858.056.856.056.760.060.462.161.664.464.366.564.766.466.865.962.664.853.544.334.323.112.50.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.1-2977.12977261126112611-1724.927-1324.618-839.903-349.592-679.92-527.0970.0
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-26.5-27.9-27.9-27.7-26.4-23.7-22.3-21.3-23.0-21.5-22.8-21.6-24.3-21.223.621.527.924.2-20.0-19.0-13.1-6.4-10.9-9.00.0
Percentage of Assets-12.2-12.5-12.1-11.9-11.7-11.4-10.9-10.8-11.3-11.3-11.8-11.7-12.4-11.412.611.413.418.2-14.5-13.1-9.3-4.3-8.00.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0124000.0129000.0129000.0129000.0129000.0128000.0128000.0128000.0128000.0128000.0128000.0127000.0127000.0127000.0129000.0128000.0128000.0127000.0125000.0124000.0144000.0
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:RetainedEarningsAccumulatedDeficit


Retained
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1390013833139761396114466156731645517065161821702616257169441549917334158101610714881147811507115030142291317912208119991103310106928384007543682963495891540449134486419437963409310628062454216618721068
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets56.858.056.856.056.760.060.462.161.664.464.366.564.766.466.869.868.469.765.968.066.163.762.657.965.866.464.861.358.455.853.552.449.848.344.343.641.437.434.331.928.526.123.112.5

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value-171.8-174.3-299.0-225.5-181.0-149.3-135.2-92.3-252.9-219.8-240.4-248.3-261.6-303.9-318.4-329.4-338.8-325.2-319.9-300.9-282.8-259.3-224.0-157.416-101.025-70.538-59.488-37.987-26.678-22.355-27.745-29.315-55.136-67.975-55.305-51.115-50.557-17.71-26.5357.57125-0.992-21.6150
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-0.7-0.7-1.2-0.9-0.7-0.6-0.5-0.3-1.0-0.8-1.0-1.0-1.1-1.2-1.3-1.4-1.6-1.5-1.4-1.4-1.3-1.3-1.1-0.8-0.6-0.5-0.4-0.3-0.2-0.2-0.2-0.3-0.5-0.7-0.5-0.5-0.6-0.2-0.30.10.3-0.0-0.30.6

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-31
Value-63.9-64.3-66.3-32.4-31.9-32.0-32.8-29.8-30.6-30.7-31.3-36.6-36.4-37.3-36.8-33.2-33.2-32.6-32.7-36.5-36.9-37.6-37.8-27.0-27.5-30.3-31.6-18.3-19.0-18.8-19.6-18.5-19.4-20.5-21.7-9.00.2
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax37.236.922.214.417.621.424.332.312.114.013.014.713.912.311.610.19.810.010.212.113.014.516.917.227.243.053.148.271.284.170.663.135.230.239.233.9-0.9
Percentage of Assets-0.3-0.3-0.3-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.2-0.1-0.2-0.1-0.2-0.2-0.1-0.2-0.2-0.2-0.2-0.1-0.2-0.2-0.2-0.1-0.1-0.2-0.2-0.2-0.2-0.2-0.2-0.10.0
Percentage of Assets us-gaap:AccumulatedDefinedBenefitPlansAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-31
Value-40.4-29.4-179.0-93.3-9.6417.8721351344.5-0.7-133.5-104.5-104.5-69.057
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax23.516.959.941.45.3-27.9-5.8-78.9-5.4-23.5-14.4-1.80.343.932.831.720.4-18.1
Percentage of Assets-0.2-0.1-0.7-0.4-0.00.20.00.30.10.20.10.0-0.0-0.5-0.4-0.5-0.30.3
Percentage of Assets us-gaap:AccumulatedGainLossNetCashFlowHedgeParent0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-31
Value0.10.61.45.25.1-3.64.26.36.22.9-4.0-1.9-1.7-2.3-1.6-4.2-5.2-12.4-10.80.86.21.7-0.8-1.60.70.9-0.40.50.47.35.6159.23.14.20.012
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax-0.1-0.3-0.5-2.3-2.82.4-3.1-6.8-2.5-1.31.70.80.60.80.51.31.53.83.4-0.3-2.2-0.70.41.0-0.7-1.30.7-1.3-1.5-32.7-20.2-52.5-16.7-4.6-7.6-0.0-57.4
Percentage of Assets0.00.00.00.00.0-0.00.00.00.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.00.00.00.0-0.0-0.00.00.0-0.00.00.00.10.00.10.10.00.00.00.2
Percentage of Assets us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncome


Accumulated
Period End2020-12-312019-12-312018-12-312017-12-31
Value-299.0-135.2-240.4-318.4
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0
Percentage of Assets-1.2-0.5-1.0-1.3
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-31
Value1113-8.5304148255029173.50.00.00.00.00.00.0
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax-6.8-8.02.8-13.6-23.1-32.2-18.6-54.6-11.5-8.0-1.5-0.0-0.0-0.0-0.0-0.0-0.0
Percentage of Assets0.00.1-0.00.10.20.20.10.20.10.10.00.00.00.00.00.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedTranslationAdjustment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-31
Value-79.2-95.1-46.6-135.6-186.5-203.4-139.5-192.0-271.4-261.1-243.3-214.3-222.8-130.8-175.5-187.5-231.4-314.2-334.2-258.4-244.0-186.0-195.6-160.5-137.0-200.1-99.2-61.2-1.07.110.0-9.9-43.5-51.5-27.1-50.3-24.4
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax46.154.615.660.1103.0136.2103.2208.0107.3118.8101.286.385.243.055.156.968.396.6104.585.986.371.787.3102.0135.6283.7166.8161.13.7-31.8-36.033.878.975.849.0189.6112.9
Percentage of Assets-0.3-0.4-0.2-0.5-0.7-0.8-0.5-0.7-1.0-1.0-1.0-0.8-0.9-0.5-0.7-0.8-1.1-1.5-1.5-1.2-1.1-0.9-1.0-0.8-0.8-1.3-0.7-0.4-0.00.10.1-0.1-0.4-0.5-0.3-0.6-0.3
Percentage of Assets us-gaap:AccumulatedTranslationAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Treasury Stock Value

us-gaap:TreasuryStockValue

us-gaap:TreasuryStockValue


Treasury
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value29772977297729772977297729772977297729772977297729772977297729772977297726112611261126112611261126112611261120842061172417241724136513651324130313031303839728728537349679
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets12.212.512.111.911.711.410.910.811.311.311.811.712.411.412.612.913.714.011.411.812.112.613.412.615.617.218.215.216.014.114.515.312.613.413.113.514.214.39.38.38.46.54.38.0

Minority Interest

us-gaap:MinorityInterest

us-gaap:MinorityInterest


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-31
Value462-19.0-14.2-14.0-19.5-10.0-4.1-4.1-4.1-7.9-8.0-6.8-7.2-16.2-14.7-11.6-11.6-11.6-11.5-2.7-0.11.32.1-5.7830.4212.6875.033.1893.9274.3520.5960.5960.5960.5962.2722.3882.3882.6471.4884.44679705239404140
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.9-0.1-0.1-0.1-0.1-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.1-0.1-0.1-0.1-0.1-0.0-0.00.00.0-0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.90.80.70.00.00.00.5

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1227769-367.111811948146719601694196414591895173510991457151816281169235157698699596310408951047733932914990104869671625178507541635194473570429253431428428336
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues44.228.5-12.935.052.941.553.447.154.341.853.850.532.846.545.952.938.08.454.933.434.435.336.632.240.428.735.336.440.94.944.236.836.312.635.839.144.715.135.743.635.521.135.436.435.330.4

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-152.7-64.7-166.4-52.4-832.7442708-365.9-110.8238-1625.3-619.1-1148.51346-769.5-1246.8-202.6-744.2-581.736-736.1-1203.2-1807.529-989.937-1253.363-502.771-378.278-540.564-630.1275.993-709.976-324.392-726.241155-375.454-522.39-53.1160.618-389.532-587.177-546.79-126.795-518.622-69.754683249
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-5.5-2.4-5.8-1.6-22.612.519.3-10.2-3.16.8-46.1-18.0-34.243.0-23.3-40.5-6.6-26.5-20.31.2-25.4-44.1-63.7-35.6-48.4-19.7-14.3-21.5-26.00.3-36.1-17.7-42.111.0-26.5-37.7-3.70.0-29.4-44.8-45.2-10.5-42.5-5.956.422.5

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-564.5-785.0-401.1-1312.9-1313.4-2245.3-2116.4-689.0-2375.7-679.3-1437.025-2791.5-268.6-708.1-19.5-751.0-901.4-721.2-300.6-13.447-1998.4032907-3.53780-513.265-35.123-322.3611411-318.522-170.763-238.424-15.524-28.25-417.44-416.264-142.809-99.12821-99.832225-461.259-1026.126-523.46
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-20.3-29.1-14.1-38.9-35.7-63.5-57.6-19.1-65.7-19.5-40.80.7-83.2-8.6-21.4-0.6-24.4-32.1-25.1-10.2-0.51.7-70.4104.7-0.13.2-19.4-1.4-13.35.40.6-17.4-9.9-16.8-1.1-2.0-29.4-32.2-10.8-7.61.8-8.318.5-39.2-84.6-47.2

Deferred Income Tax Expense Benefit

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:DeferredIncomeTaxExpenseBenefit


Deferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-607.8-15.0-62.9311433638-43.2-156.422815312-110.553131-19.2-96.676-118.2-26.6-39.18.940-95.155-107.38616-78.949-82.767-66.948-79.558-78.89-48.14-51.522-66.525-30.042-43.027-39.955-3.8763767-23.34871-20.166-30.927-38.3598.042
Percentage of DeferredIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization

us-gaap:DepreciationDepletionAndAmortization


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
Value721469013411211911332911712132934617116889177302512177180175149156151144147157175164190158147128979694
Percentage of DepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Increase Decrease In Accounts Receivable

us-gaap:IncreaseDecreaseInAccountsReceivable

us-gaap:IncreaseDecreaseInAccountsReceivable


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-174.3-37.2-138.5-133.130238-71.2-0.5-133.7136-48.86653134209-75.41051953.3173-95.0160-92.60824-89.38128215108-8.724197-93.107341107514-29.244-78.3088956-37.575-35.8039026492.75420
Percentage of IncreaseDecreaseInAccountsReceivable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Increase Decrease In Inventories

us-gaap:IncreaseDecreaseInInventories

us-gaap:IncreaseDecreaseInInventories


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value81112458212662666120-129.020-8.242-2.6-75.885394610263988246959216647551661536860573825192311186.498205.136-9.183-12.264
Percentage of IncreaseDecreaseInInventories100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Increase Decrease In Other Operating Capital Net

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value1680-273.71068.6-18.52.3-19.3-90.8171-86.789-28.720-18.2621533448-12.0-35.3-14.8-90.55955-3.3376953-66.835-31.40775182-129.402-33.654-35.2127.282-38.2625020-53.648-9.34575-6.638
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1227769-367.111811948146719601694196414591895173510991457151816281169235157698699596310408951047733932914990104869671625178507541635194473570429253431428428336
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues44.228.5-12.935.052.941.553.447.154.341.853.850.532.846.545.952.938.08.454.933.434.435.336.632.240.428.735.336.440.94.944.236.836.312.635.839.144.715.135.743.635.521.135.436.435.330.4

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value44841035770115421399143915451494140894614448661172-297.4122686274764910321049970831965927822883856714479457487490426292398386302300351288294240254293217305277142244
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues16.215.212.520.841.939.639.242.941.340.426.842.025.837.5-9.039.828.026.622.634.936.335.629.334.835.832.233.534.129.522.523.326.728.530.220.628.827.223.422.626.923.824.519.721.624.219.627.124.813.123.5

us-gaap:NetIncomeLoss us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value-27.6-21.4-17.7-6.62714403731169.8-8.7-10.7-37.4-28.9-18.8-2.86.34.7-5.3-4.78.753424034132.70.7-4.20.2-7.2-0.1
Percentage of NetIncomeLoss-6.2-5.2-4.9-0.91.81.12.82.42.11.21.0-0.6-1.2-3.29.7-1.5-0.30.80.7-0.5-0.40.96.44.44.34.21.50.30.1-0.90.0-1.5-0.0
Percentage of Revenues-1.0-0.8-0.6-0.20.80.41.11.00.90.50.3-0.3-0.3-1.2-0.9-0.6-0.10.20.2-0.2-0.20.31.91.51.51.40.50.10.0-0.20.0-0.4-0.0
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Profit Loss

us-gaap:ProfitLoss

us-gaap:ProfitLoss


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value102540435770316061392143915451494140894414429151171-166.31226862747647103010489698281019924820882856723479457487490426292398387302300353304308271112294220306279144246
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues37.015.012.520.843.639.439.242.941.340.426.842.027.337.4-5.039.828.026.622.634.936.235.529.236.735.732.133.434.129.922.523.326.728.530.220.628.827.223.422.627.025.225.722.39.524.319.827.225.013.323.8

us-gaap:ProfitLoss us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312011-12-312011-09-302011-06-302010-12-312010-09-302010-06-30
Value577-5.6-0.32.464-6.5-0.0421.91631-141.91.2
Percentage of ProfitLoss56.3-1.4-0.10.34.0-0.5-0.00.55.311.6-126.50.4
Percentage of Revenues20.8-0.2-0.00.11.7-0.2-0.00.11.32.6-12.10.1
Percentage of Revenues us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value44841035770115421399143915451494
Percentage of ProfitLoss43.7101.4100.199.796.0100.5100.0100.0100.0
Percentage of Revenues16.215.212.520.841.939.639.242.941.3
Percentage of Revenues us-gaap:Parent0.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value44841035770115421399143915451494
Percentage of ProfitLoss43.7101.4100.199.796.0100.5100.0100.0100.0
Percentage of Revenues16.215.212.520.841.939.639.242.941.3
Percentage of Revenues us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.0

Share Based Compensation

us-gaap:ShareBasedCompensation

us-gaap:ShareBasedCompensation


Share
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value54704933486738455245383738433030303737333845293741523535374631373036302728322629243333394451
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-152.7-64.7-166.4-52.4-832.7442708-365.9-110.8238-1625.3-619.1-1148.51346-769.5-1246.8-202.6-744.2-581.736-736.1-1203.2-1807.529-989.937-1253.363-502.771-378.278-540.564-630.1275.993-709.976-324.392-726.241155-375.454-522.39-53.1160.618-389.532-587.177-546.79-126.795-518.622-69.754683249
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-5.5-2.4-5.8-1.6-22.612.519.3-10.2-3.16.8-46.1-18.0-34.243.0-23.3-40.5-6.6-26.5-20.31.2-25.4-44.1-63.7-35.6-48.4-19.7-14.3-21.5-26.00.3-36.1-17.7-42.111.0-26.5-37.7-3.70.0-29.4-44.8-45.2-10.5-42.5-5.956.422.5

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value71928684105149110901861272251631861942302291972101821701361261862291299710662645478805433695872547051543248384738
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-564.5-785.0-401.1-1312.9-1313.4-2245.3-2116.4-689.0-2375.7-679.3-1437.025-2791.5-268.6-708.1-19.5-751.0-901.4-721.2-300.6-13.447-1998.4032907-3.53780-513.265-35.123-322.3611411-318.522-170.763-238.424-15.524-28.25-417.44-416.264-142.809-99.12821-99.832225-461.259-1026.126-523.46
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-20.3-29.1-14.1-38.9-35.7-63.5-57.6-19.1-65.7-19.5-40.80.7-83.2-8.6-21.4-0.6-24.4-32.1-25.1-10.2-0.51.7-70.4104.7-0.13.2-19.4-1.4-13.35.40.6-17.4-9.9-16.8-1.1-2.0-29.4-32.2-10.8-7.61.8-8.318.5-39.2-84.6-47.2

Proceeds From Issuance Of Long Term Debt

us-gaap:ProceedsFromIssuanceOfLongTermDebt

us-gaap:ProceedsFromIssuanceOfLongTermDebt


Proceeds
Period End2020-12-312020-09-30
Value0.10.0
Percentage of ProceedsFromIssuanceOfLongTermDebt100.00.0

Payments For Repurchase Of Common Stock

us-gaap:PaymentsForRepurchaseOfCommonStock

us-gaap:PaymentsForRepurchaseOfCommonStock


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value4506004001250280822202093717240165513520.027502500.00.07815836513480.00.020012955526233360.00.001-359.30.04121534464631110.01911950.04681031577
Percentage of PaymentsForRepurchaseOfCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.00.00.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.00.0100.0100.00.0100.0100.0100.0

us-gaap:PaymentsForRepurchaseOfCommonStock us-gaap:ShareRepurchaseProgram

biib:December2019ShareRepurchaseProgram


Payments
Period End2021-06-302020-09-302020-06-302020-03-31
Value280013002800941
Percentage of PaymentsForRepurchaseOfCommonStock622.2104.099.742.4

biib:March2019ShareRepurchaseProgram


Payments
Period End2020-09-302020-06-302020-03-31
Value0.013001300
Percentage of PaymentsForRepurchaseOfCommonStock0.046.358.6

biib:October2020ShareRepurchaseProgram


Payments
Period End2021-06-302021-03-31
Value450600
Percentage of PaymentsForRepurchaseOfCommonStock100.0100.0

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations

us-gaap:EffectiveIncomeTaxRateContinuingOperations


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-70.39.5-1.225.10.2190.17200.1190.1410.2270.0290.2040.2240.2160.240.2380.2380.242-0.0050.2470.2520.269-0.0020.2430.2390.256-0.0070.2420.270.2680.0170.2740.2440.1320.0190.2470.2380.21400.2640.2380.276-0.0180.4010.2580.255
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Liabilities

us-gaap:DeferredTaxLiabilities

us-gaap:DeferredTaxLiabilities


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value194134842305358490542539691609598567597
Percentage of DeferredTaxLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Net

us-gaap:DeferredTaxAssetsNet

us-gaap:DeferredTaxAssetsNet


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value2278390528238311071871693540421357478445
Percentage of DeferredTaxAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Unrecognized Tax Benefits

us-gaap:UnrecognizedTaxBenefits

us-gaap:UnrecognizedTaxBenefits


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value7512911466326713111012564121147249221
Percentage of UnrecognizedTaxBenefits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Valuation Allowance

us-gaap:DeferredTaxAssetsValuationAllowance

us-gaap:DeferredTaxAssetsValuationAllowance


Deferred
Period End2021-06-302020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value37517531.120161614111.51210100.0
Percentage of DeferredTaxAssetsValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

biib:AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears

biib:AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value183012149.4165.80.117244.916-6.2-3.5-3.6-0.9-6.34.8-10.1204.91.4-4.79.59.0181314-11.7-0.98.33.96.3-2.5-0.7-0.12.83.14.81.72.06.4
Percentage of AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears us-gaap:ValuationAllowancesAndReservesType

biib:ContractualAdjustments


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value193212159.8157.44.816253.014-5.4-2.0-3.8-1.1-9.3-0.8-12.512-0.5-1.1-4.61.19.6101024-9.72.18.63.57.4-3.1-0.6-0.42.23.54.61.03.05.4
Percentage of AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears104.3106.396.1109.7104.394.1127.64800.093.9102.461.285.287.157.1105.6122.2147.6-16.7123.861.5-10.2-78.697.911.6106.755.179.7172.982.9-233.3103.689.7117.5124.085.7400.078.6112.995.858.8150.084.4

biib:ReserveforCashDiscounts


Adjustments
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-0.2-0.90.0-0.30.80.5-0.70.00.7-0.30.00.0
Percentage of AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears-1.1-3.00.0-2.18.53.0-12.10.03.9-1.20.00.0

us-gaap:SalesReturnsAndAllowances


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-03-31
Value-0.6-1.00.5-1.1-1.20.5-0.9-4.70.4-0.31.92.5-2.3-0.30.30.22.16.33.47.95.6-0.1-0.16.72.25.91.9-10.0-1.0-4.4-0.20.3-1.0-0.2-0.2-0.70.21.0
Percentage of AdjustmentsToProductRevenueReservesRelatingToSalesInPriorYears-3.2-3.33.9-7.6-12.83.0-15.5-4700.02.2-1.238.814.837.18.6-8.3-22.2-33.3131.2-33.738.5114.3-7.12.170.524.431.914.3-71.48.5488.9-2.47.7-15.98.028.6-22.64.215.6

biib:AmortizationAndImpairmentOfAcquiredIntangibleAssets

biib:AmortizationAndImpairmentOfAcquiredIntangibleAssets


Amortization
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value60498826171283
Percentage of AmortizationAndImpairmentOfAcquiredIntangibleAssets100.0100.0100.0100.0100.0100.0

biib:AmortizationAndImpairmentOfAcquiredIntangibleAssets us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:InProcessResearchAndDevelopment


Amortization
Period End2020-09-302019-09-30
Value19215
Percentage of AmortizationAndImpairmentOfAcquiredIntangibleAssets23.476.0

biib:Biogenshareofcopromotionprofitsorlosses us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

biib:Biogenshareofcopromotionprofitsorlosses

biib:SamsungBiosimilarAgreement


Biogenshareofcopromotionprofitsorlossesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302018-09-302018-06-302018-03-31
Value050.049.500.50000.5
Percentage of Biogenshareofcopromotionprofitsorlosses0.0100.0100.00.0100.00.00.00.0100.0

biib:Collaborationprofitlosssharing

biib:Collaborationprofitlosssharing


Collaborationprofitlosssharing
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-30
Value-15.2687321716063584739423526204.7-5.60.00.00.0
Percentage of Collaborationprofitlosssharing100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

biib:Collaborationprofitlosssharing us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

biib:SamsungBiosimilarAgreement


Collaborationprofitlosssharingus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-30
Value69687255716063584739433425207.4
Percentage of Collaborationprofitlosssharing-459.9100.099.9254.1100.099.899.8100.0100.4101.3103.198.095.1100.0157.4

biib:CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear

biib:CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear


Current
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value9959641032104898810331052935884826922833826806794711705707724685641616593553529553462429374378341312280176197167141146122121109119
Percentage of CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear us-gaap:ValuationAllowancesAndReservesType

biib:ContractualAdjustments


Current
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value80177584384179682786175871068073766164664162656155156850956149348045442341344135133028429330121819313716313311010993928391
Percentage of CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear80.580.481.780.380.680.181.981.180.482.379.979.378.379.578.978.978.380.470.381.977.077.876.676.578.079.876.076.975.877.588.270.169.277.782.779.677.975.276.276.475.976.8

biib:ReserveforCashDiscounts


Current
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
Value190185185202186200185171167141180165
Percentage of CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear19.119.217.919.318.919.417.718.319.017.119.619.9

us-gaap:SalesReturnsAndAllowances


Current
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value3.63.84.24.95.24.74.85.55.94.75.16.65.65.86.94.87.67.67.55.88.98.7117.38.91011127.67.16.96.26.13.74.75.41.6104.74.23.03.8
Percentage of CurrentProvisionsToProductRevenueReservesRelatingToSalesInCurrentYear0.40.40.40.50.50.50.50.60.70.60.60.80.70.70.90.71.11.11.00.81.41.41.91.31.71.82.52.92.01.92.02.02.22.12.43.21.17.03.93.52.73.2

biib:DebtInstrumentRedemptionAmount us-gaap:DebtInstrument

biib:DebtInstrumentRedemptionAmount

biib:SeniorNotesFivePointTwoPercentDueTwentyFortyFive


Debt
Period End2021-02-28
Value8900000.0
Percentage of DebtInstrumentRedemptionAmount100.0

biib:DeferredTaxAssetIncreaseDecreaseInValue us-gaap:ProductOrService

biib:DeferredTaxAssetIncreaseDecreaseInValue

biib:TECFIDERA


Deferred
Period End2021-06-30
Value92
Percentage of DeferredTaxAssetIncreaseDecreaseInValue100.0

biib:Derivativesusedinnetinvestmenthedgenetoftaxexcludedcomponentincreasedecrease us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship

biib:Derivativesusedinnetinvestmenthedgenetoftaxexcludedcomponentincreasedecrease

us-gaap:NetInvestmentHedging


Derivativesusedinnetinvestmenthedgenetoftaxexcludedcomponentincreasedecreaseus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value300000.0-1400000.01400000.0-200000.03500000.0-300000.0-4800000.01400000.02300000.04400000.00000
Percentage of Derivativesusedinnetinvestmenthedgenetoftaxexcludedcomponentincreasedecrease100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

biib:EarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCosts us-gaap:DebtInstrument, us-gaap:LongtermDebtType

biib:EarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCosts

biib:A2.90SeniorNotesDueSept152020, us-gaap:SeniorNotes


Early
Period End2021-06-302021-03-31
Value0.012
Percentage of EarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCosts0.0100.0

biib:EffectiveTaxRateReconciliationGILTItax

biib:EffectiveTaxRateReconciliationGILTItax


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1.50.902.20.0150.006-0.0010.0160.0140.0190.0020.0130.0180.013
Percentage of EffectiveTaxRateReconciliationGILTItax100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:EffectiveTaxRateReconciliationNuerImmuneTaxImpacts

biib:EffectiveTaxRateReconciliationNuerImmuneTaxImpacts


Effective
Period End2021-06-302020-06-30
Value-83.1-0.2
Percentage of EffectiveTaxRateReconciliationNuerImmuneTaxImpacts100.0100.0

biib:ExpenseIncurredByCollaboration us-gaap:ProductOrService, us-gaap:TypeOfArrangement

biib:ExpenseIncurredByCollaboration

biib:E2609andBAN2401, biib:Eisai


Expense
Period End2021-06-302020-06-30
Value6233
Percentage of ExpenseIncurredByCollaboration100.0100.0

biib:ExpenseIncurredByCollaboration us-gaap:TypeOfArrangement

biib:Eisai


Expense
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value55667533434316868
Percentage of ExpenseIncurredByCollaboration0.00.00.0100.00.00.00.00.0

biib:Expenseincurredbythecollaboration us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement

biib:Expenseincurredbythecollaboration

us-gaap:ResearchAndDevelopmentExpense, biib:DenaliTherapeuticsInc


Expenseincurredbythecollaborationus-gaap:
Period End2021-06-30
Value10
Percentage of Expenseincurredbythecollaboration100.0

us-gaap:ResearchAndDevelopmentExpense, biib:SageTherapeuticsInc


Expenseincurredbythecollaborationus-gaap:
Period End2021-06-30
Value54
Percentage of Expenseincurredbythecollaboration519.2

us-gaap:ResearchAndDevelopmentExpense, biib:UCBPharmaS.A.


Expenseincurredbythecollaborationus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value1616106.519
Percentage of Expenseincurredbythecollaboration154.80.00.00.00.0

us-gaap:SellingGeneralAndAdministrativeExpenses, biib:SageTherapeuticsInc


Expenseincurredbythecollaborationus-gaap:
Period End2021-06-30
Value10
Percentage of Expenseincurredbythecollaboration101.0

biib:Expenseincurredbythecollaboration us-gaap:ProductOrService, us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement

biib:ADUHELM, us-gaap:ResearchAndDevelopmentExpense, biib:Eisai


Expenseincurredbythecollaborationus-gaap:
Period End2021-06-302020-06-30
Value4235
Percentage of Expenseincurredbythecollaboration404.80.0

biib:ADUHELM, us-gaap:SellingGeneralAndAdministrativeExpenses, biib:Eisai


Expenseincurredbythecollaborationus-gaap:
Period End2021-06-302020-06-30
Value12545
Percentage of Expenseincurredbythecollaboration1207.70.0

biib:Aducanumab, us-gaap:ResearchAndDevelopmentExpense, biib:Eisai


Expenseincurredbythecollaborationus-gaap:
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value47593735198.94.73.216260647663667374
Percentage of Expenseincurredbythecollaboration0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:Aducanumab, us-gaap:SellingGeneralAndAdministrativeExpenses, biib:Eisai


Expenseincurredbythecollaborationus-gaap:
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value1111949045226.10.10.2201712147.18.75.14.8
Percentage of Expenseincurredbythecollaboration0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:E2609andBAN2401, us-gaap:SellingGeneralAndAdministrativeExpenses, biib:Eisai


Expenseincurredbythecollaborationus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value4.35.73.50.01.44.97.610
Percentage of Expenseincurredbythecollaboration41.30.00.00.00.00.00.00.0

biib:Expensereflectedwithinstatementsofincome us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement

biib:Expensereflectedwithinstatementsofincome

us-gaap:ResearchAndDevelopmentExpense, biib:DenaliTherapeuticsInc


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-30
Value6.2
Percentage of Expensereflectedwithinstatementsofincome100.0

us-gaap:ResearchAndDevelopmentExpense, biib:SageTherapeuticsInc


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-30
Value27
Percentage of Expensereflectedwithinstatementsofincome435.5

us-gaap:ResearchAndDevelopmentExpense, biib:UCBPharmaS.A.


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value8.18.45.23.29.5
Percentage of Expensereflectedwithinstatementsofincome130.60.00.00.00.0

us-gaap:SellingGeneralAndAdministrativeExpenses, biib:SageTherapeuticsInc


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-30
Value5.2
Percentage of Expensereflectedwithinstatementsofincome83.9

biib:Expensereflectedwithinstatementsofincome us-gaap:ProductOrService, us-gaap:IncomeStatementLocation, us-gaap:TypeOfArrangement

biib:ADUHELM, us-gaap:ResearchAndDevelopmentExpense, biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-302020-06-30
Value2319
Percentage of Expensereflectedwithinstatementsofincome374.20.0

biib:ADUHELM, us-gaap:SellingGeneralAndAdministrativeExpenses, biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-302020-06-30
Value6725
Percentage of Expensereflectedwithinstatementsofincome1090.30.0

biib:Aducanumab, us-gaap:ResearchAndDevelopmentExpense, biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value25322019104.92.61.78951556563667374
Percentage of Expensereflectedwithinstatementsofincome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:Aducanumab, us-gaap:SellingGeneralAndAdministrativeExpenses, biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value601045125123.40.00.1118.35.19.23.98.75.14.8
Percentage of Expensereflectedwithinstatementsofincome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:E2609andBAN2401, us-gaap:SellingGeneralAndAdministrativeExpenses, biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value2.12.91.70.00.72.43.85.1
Percentage of Expensereflectedwithinstatementsofincome33.90.00.00.00.00.00.00.0

biib:Expensereflectedwithinstatementsofincome us-gaap:ProductOrService, us-gaap:TypeOfArrangement

biib:ADUHELM, biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-302020-06-30
Value4533
Percentage of Expensereflectedwithinstatementsofincome725.80.0

biib:E2609andBAN2401, biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-06-302020-06-302019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value31178434343227261914
Percentage of Expensereflectedwithinstatementsofincome501.60.00.00.00.00.00.00.00.00.0

biib:Expensereflectedwithinstatementsofincome us-gaap:TypeOfArrangement

biib:Eisai


Expensereflectedwithinstatementsofincomeus-gaap:
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value2733371721218434
Percentage of Expensereflectedwithinstatementsofincome0.00.00.00.00.00.00.00.0

biib:GlobalLicensingCollaborationAgreementAmountSharesPurchased us-gaap:TypeOfArrangement

biib:GlobalLicensingCollaborationAgreementAmountSharesPurchased

biib:DenaliTherapeuticsInc


Global
Period End2021-06-302021-03-312020-09-30
Value0.0465465
Percentage of GlobalLicensingCollaborationAgreementAmountSharesPurchased0.0100.0100.0

biib:SageTherapeuticsInc


Global
Period End2020-11-30
Value650
Percentage of GlobalLicensingCollaborationAgreementAmountSharesPurchased0.0

biib:GlobalLicensingCollaborationAgreementPurchasePricePerShare us-gaap:TypeOfArrangement

biib:GlobalLicensingCollaborationAgreementPurchasePricePerShare

biib:DenaliTherapeuticsInc


Global
Period End2020-09-30
Value34.94
Percentage of GlobalLicensingCollaborationAgreementPurchasePricePerShare100.0

biib:GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryAndCommercialMilestonePayments us-gaap:TypeOfArrangement

biib:GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryAndCommercialMilestonePayments

biib:DenaliTherapeuticsInc


Global
Period End2020-09-30
Value1100
Percentage of GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryAndCommercialMilestonePayments100.0

biib:SageTherapeuticsInc


Global
Period End2020-11-30
Value1600
Percentage of GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryAndCommercialMilestonePayments0.0

biib:GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryandCommercialMilestonePayments us-gaap:TypeOfArrangement

biib:GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryandCommercialMilestonePayments

biib:DenaliTherapeuticsInc


Global
Period End2021-06-302021-03-31
Value0.01100
Percentage of GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryandCommercialMilestonePayments0.0100.0

biib:SageTherapeuticsInc


Global
Period End2020-11-30
Value1600
Percentage of GlobalLicensingCollaborationAgreementResearchDevelopmentRegulatoryandCommercialMilestonePayments0.0

biib:GlobalLicensingCollaborationAgreementSharesPurchased us-gaap:TypeOfArrangement

biib:GlobalLicensingCollaborationAgreementSharesPurchased

biib:DenaliTherapeuticsInc


Global
Period End2020-09-30
Value13
Percentage of GlobalLicensingCollaborationAgreementSharesPurchased100.0

biib:SageTherapeuticsInc


Global
Period End2020-11-30
Value6.2
Percentage of GlobalLicensingCollaborationAgreementSharesPurchased0.0

biib:GlobalLicensingCollaborationAgreementSharesPurchasedPerShare us-gaap:TypeOfArrangement

biib:GlobalLicensingCollaborationAgreementSharesPurchasedPerShare

biib:DenaliTherapeuticsInc


Global
Period End2021-06-302021-03-31
Value034.94
Percentage of GlobalLicensingCollaborationAgreementSharesPurchasedPerShare0.0100.0

biib:IncomeLossFromEquityMethodInvestmentsNetOfTax

biib:IncomeLossFromEquityMethodInvestmentsNetOfTax


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value34-18.218-13.115-14.8-12.6-21.8
Percentage of IncomeLossFromEquityMethodInvestmentsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0

biib:IncomeTaxExpenseReductioninDeferredTaxAssetsandLiabilitiesNet us-gaap:ProductOrService

biib:IncomeTaxExpenseReductioninDeferredTaxAssetsandLiabilitiesNet

biib:TECFIDERA


Income
Period End2020-09-302020-06-30
Value3356
Percentage of IncomeTaxExpenseReductioninDeferredTaxAssetsandLiabilitiesNet100.0100.0

biib:LongTermDebtExchangedAmount us-gaap:DebtInstrument

biib:LongTermDebtExchangedAmount

biib:A3250SeniorNotesDueFebruary152051


Long
Period End2021-02-28
Value700
Percentage of LongTermDebtExchangedAmount100.0

biib:SeniorNotesFivePointTwoPercentDueTwentyFortyFive


Long
Period End2021-02-28
Value624
Percentage of LongTermDebtExchangedAmount89.1

biib:NoncontrollingInterestCapitalContribution

biib:NoncontrollingInterestCapitalContribution


Noncontrolling
Period End2021-06-30
Value5000000.0
Percentage of NoncontrollingInterestCapitalContribution100.0

biib:NoncontrollingInterestCapitalContribution us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Noncontrolling
Period End2021-06-30
Value5000000.0
Percentage of NoncontrollingInterestCapitalContribution100.0

biib:NoncontrollingInterestIncreaseDecreaseOther

biib:NoncontrollingInterestIncreaseDecreaseOther


Noncontrolling
Period End2021-06-30
Value-100000000.0
Percentage of NoncontrollingInterestIncreaseDecreaseOther100.0

biib:NoncontrollingInterestIncreaseDecreaseOther us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Noncontrolling
Period End2021-06-30
Value-100000000.0
Percentage of NoncontrollingInterestIncreaseDecreaseOther100.0

biib:Noncontrollinginterestincreasedecreaseother

biib:Noncontrollinginterestincreasedecreaseother


Noncontrollinginterestincreasedecreaseother
Period End2021-03-312020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value0.1794.0-75.00.00.04.20.1130.10.50.2150.00.00.01.40.10.00.00.30.20.16.70.00.00.0
Percentage of Noncontrollinginterestincreasedecreaseother100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.0100.00.00.0100.0100.0100.0100.00.00.00.0

biib:Noncontrollinginterestincreasedecreaseother us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Noncontrollinginterestincreasedecreaseotherus-gaap:
Period End2021-03-312020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0.1794.0-75.00.00.04.20.10.81.911
Percentage of Noncontrollinginterestincreasedecreaseother100.0100.0100.0100.00.00.0100.0100.06.01900.02220.0

biib:OtherrevenuesfromantiCD20therapeuticprograms us-gaap:MajorCustomers

biib:OtherrevenuesfromantiCD20therapeuticprograms

biib:RocheGroupGenentech


Otherrevenuesfromanti
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value26121421228522017921920219912616915313193948149
Percentage of OtherrevenuesfromantiCD20therapeuticprograms100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToCurrentYear

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToCurrentYear


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value7853968988928863839188427232947807066542996857105422946336505532625155084252174313633191222982661216315913411344114101
Percentage of PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToCurrentYear100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToCurrentYear us-gaap:ValuationAllowancesAndReservesType

biib:ContractualAdjustments


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value62228472168570831073268259323360155350422752957741823144652441718738638731716632927323891254177844412910283318776
Percentage of PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToCurrentYear79.271.880.376.979.980.979.881.082.179.377.178.477.076.077.381.277.178.870.580.675.471.675.076.374.676.676.375.274.774.885.166.669.569.681.376.573.771.076.576.1

biib:ReserveforCashDiscounts


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value1631111772061787318615912860178151
Percentage of PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToCurrentYear20.828.219.723.120.119.120.319.017.820.622.821.4

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value1556471164419954915701644742240171412156012133733128163283301589216-2.377572089.85.250100103.526736.410
Percentage of PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear us-gaap:ValuationAllowancesAndReservesType

biib:ContractualAdjustments


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value1135621044518043211591273781125143326105211126725125155229241684170-7.168411597.20.444836.3-0.322602.86.8
Percentage of PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear73.286.989.9101.890.278.777.384.577.479.650.262.983.479.169.786.392.279.374.998.094.981.180.6109.794.278.8308.787.973.176.373.57.788.283.158.3-8.684.882.243.867.3

biib:ReserveforCashDiscounts


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value36828.000000000000014-6.214112-1.67.429921.36.8
Percentage of PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear23.512.86.9-13.97.220.4-10.710.618.119.45.916.7

us-gaap:SalesReturnsAndAllowances


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value5.21.73.85.45.24.85.03.57.34.69.78.34.88.75.95.56.35.43.75.74.95.52.61.13.24.64.18.6128.33.24.85.23.94.54.03.72.32.94.0
Percentage of PaymentsReturnsAppliedAgainstProductRevenueReservesRelatingToPriorYear3.40.33.312.12.60.933.35.04.41.043.920.42.82.138.89.05.21.610.94.43.01.98.67.13.62.1-178.311.121.24.032.792.310.43.941.7114.313.83.145.339.6

biib:PretaxChargePaymentofEarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCostsNetofDerivativeGain us-gaap:DebtInstrument, us-gaap:IncomeStatementLocation, us-gaap:LongtermDebtType

biib:PretaxChargePaymentofEarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCostsNetofDerivativeGain

biib:A2.90SeniorNotesDueSept152020, us-gaap:InterestExpense, us-gaap:SeniorNotes


Pretax
Period End2021-06-302021-03-31
Value09400000.0
Percentage of PretaxChargePaymentofEarlyCallPremiumandWriteoffofRemainingUnamortizedDebtIssuanceCostsNetofDerivativeGain0.0100.0

biib:ResearchAndDevelopmentCostsPercentage us-gaap:ConsolidatedEntities

biib:ResearchAndDevelopmentCostsPercentage

biib:Neurimmune


Research
Period End2021-06-302021-03-31
Value0100.0
Percentage of ResearchAndDevelopmentCostsPercentage0.0100.0

biib:ShareBasedCompensationExpenseIncludedInCostsAndExpenses

biib:ShareBasedCompensationExpenseIncludedInCostsAndExpenses


Share
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value577548374474424780463646404740403445425045513725468756565574645866574544414737353538474148
Percentage of ShareBasedCompensationExpenseIncludedInCostsAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:ShareOfCoPromotionProfits us-gaap:MajorCustomers

biib:ShareOfCoPromotionProfits

biib:RocheGroupGenentech


Share
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value178174206275257341381393377390365358359349320325347323
Percentage of ShareOfCoPromotionProfits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:TechnologicalAndRegulatorySuccessProbability

biib:TechnologicalAndRegulatorySuccessProbability


Technological
Period End2021-06-302021-03-31
Value021.7
Percentage of TechnologicalAndRegulatorySuccessProbability0.0100.0

us-gaap:AllocatedShareBasedCompensationExpenseNetOfTax

us-gaap:AllocatedShareBasedCompensationExpenseNetOfTax


Allocated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value597849394576434982493850425042433648465350543928489158585876666069
Percentage of AllocatedShareBasedCompensationExpenseNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationAsset1

us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationAsset1


Business
Period End2020-12-312020-09-30
Value-10.261
Percentage of BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationAsset1100.0100.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value510-80.7-934.6-184.2-197.6-335.1552640-522.51019
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtSecuritiesAvailableForSaleRealizedGain

us-gaap:DebtSecuritiesAvailableForSaleRealizedGain


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value0.10.24.91.06.15.73.70.71.00.60.20.40.81.80.31.2
Percentage of DebtSecuritiesAvailableForSaleRealizedGain100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtSecuritiesAvailableForSaleRealizedLoss

us-gaap:DebtSecuritiesAvailableForSaleRealizedLoss


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value0.50.70.80.95.2190.80.10.30.30.90.60.89.41.21.3
Percentage of DebtSecuritiesAvailableForSaleRealizedLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Depreciation

us-gaap:Depreciation


Depreciation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value5448505151484545475275646465
Percentage of Depreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation

us-gaap:DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet

us-gaap:ForeignExchangeContract, biib:Cashflowsoperatingexpenses, us-gaap:OperatingExpense


Derivative
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1.50.0-0.1-1.3-0.8-0.7-0.5-0.4-0.3-0.41.3-0.10.50.3-0.1
Percentage of DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ForeignExchangeContract, biib:Cashflowsrevenue, us-gaap:Sales


Derivative
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-9.12327383529149.2-8.4-10.4-32.9-17.4-18.8-3.06.7
Percentage of DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet-606.70.0-27000.0-2984.6-4400.0-4257.1-2960.0-2300.02800.02600.0-2530.817400.0-3760.0-1000.0-6700.0

us-gaap:DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation

us-gaap:DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet

us-gaap:ForeignExchangeContract, biib:Cashflowsoperatingexpenses, us-gaap:OperatingExpense


Derivative
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-0.8-0.2-0.91.00.4-0.3-0.9-0.10.4-0.1-0.3
Percentage of DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ForeignExchangeContract, biib:Cashflowsrevenue, us-gaap:Sales


Derivative
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value35-1.69.3-5.30.83.73.73.50.37.9-0.9
Percentage of DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet-4400.0800.0-1033.3-530.0200.0-1233.3-411.1-3500.075.0-7900.0300.0

us-gaap:DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation

us-gaap:NetInvestmentHedging, us-gaap:OtherNonoperatingIncomeExpense


Derivative
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.90.80.90.42.22.22.21.50.00.00.0
Percentage of DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet-112.5-400.0-100.040.0550.0-733.3-244.4-1500.00.0-0.0-0.0

us-gaap:DiscontinuedOperationTaxEffectOfDiscontinuedOperation us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:DiscontinuedOperationTaxEffectOfDiscontinuedOperation

biib:DenmarkManufacturingOperations


Discontinued
Period End2020-09-302020-06-302020-03-312019-12-312019-09-30
Value3.42.2594.23.4
Percentage of DiscontinuedOperationTaxEffectOfDiscontinuedOperation100.0100.0100.0100.0100.0

us-gaap:EffectOfExchangeRateOnCashAndCashEquivalents

us-gaap:EffectOfExchangeRateOnCashAndCashEquivalents


Effect
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value14-33.024-8.81217-19.52.7-0.44.8-5.4-17.1-0.9-15.016297.9-32.00.6-15.015-15.442-6.1713-37.895-22.677-15.262-3.510.5454.5416.2960.997-3.8752.0693.768-6.3534.618-2.231-6.6042.0684.126-5.5198.567-4.916-5.502
Percentage of EffectOfExchangeRateOnCashAndCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential

us-gaap:EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value-7.7-10.90.3-3.0-0.034-0.0410.002-0.05-0.046-0.046-0.020.0080-0.0070.003-0.114-0.117-0.112-0.002-0.101-0.1-0.0810.001-0.107-0.111-0.084-0.006-0.093-0.087-0.0840.01-0.066-0.072-0.0990.014-0.071-0.076-0.082-0.005-0.038-0.073-0.056
Percentage of EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciationAndAmortization

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciationAndAmortization


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-0.80.8-0.12.90.0020.00200.0040.0040.0030.0070.0030.0060.0060.0010.0120.0140.0140.0010.0120.0110.011-0.0020.0150.0110.010.0010.0070.0120.015-0.0010.0190.0180.01100.0130.0110.01100.0110.0140.0140.0010.0290.015
Percentage of EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciationAndAmortization100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseImpairmentLosses

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseImpairmentLosses


Effective
Period End2020-12-312020-09-302020-06-302019-06-30
Value-0.13.50.0270
Percentage of EffectiveIncomeTaxRateReconciliationNondeductibleExpenseImpairmentLosses100.0100.0100.00.0

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther

us-gaap:EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther


Effective
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-0.60.0010.0020-0.0010.0040.00400.0030.0040.00400.0060.0070.00700.0020.0060.0060.0010.0050.0090.0060.0010.0040.0040.003-0.002-0.003-0.010.0550.002-0.021-0.024-0.0390-0.012-0.011-0.0130.001-0.038-0.017
Percentage of EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationOtherAdjustments

us-gaap:EffectiveIncomeTaxRateReconciliationOtherAdjustments


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.40.6-1.10.50.004-0.0030.002-0.0080.005-0.0020.004-0.010.0050.002-0.0060.0040.0060.0100.0050.0030.003000.0040.0010.003-0.0120.0040.005-0.002-0.004-0.002-0.0020-0.0050.0020.0020.001-0.009-0.005-0.023-0.008-0.0010.002-0.007
Percentage of EffectiveIncomeTaxRateReconciliationOtherAdjustments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes

us-gaap:EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1.30.80.10.90.0040.0060.0010.0090.0090.004-0.0010.0060.0060.0090.0020.0070.0080.001-0.0010.0110.010.0100.0120.004-0.00400.0120.0110.012-0.0060.0250.0190.0770.0010.0080.0080.0080.0030.0130.0040.024-0.0030.0240.0190.019
Percentage of EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationTaxCredits

us-gaap:EffectiveIncomeTaxRateReconciliationTaxCredits


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value2.93.7-0.12.30.010.010.0010.0150.0090.0080.0010.010.0070.00800.0070.0090.0070.0010.0140.012-0.012-0.004-0.011-0.007-0.007-0.003-0.006-0.007-0.0130.004-0.022-0.035-0.0330.002-0.034-0.039-0.037-0.006-0.051-0.041-0.021-0.008-0.043-0.016-0.016
Percentage of EffectiveIncomeTaxRateReconciliationTaxCredits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount

us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount


Employee
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1.72.61.31.91.51.51.11.72.83.31.83.52.83.42.02.52.42.7-25.33.24.43.1-19.42.82.23.4-17.52.32.62.6-2.4-2.4-2.7-2.3-1.4-1.51.31.27.8-1.3-1.0-1.0-1.0-0.9-0.7-0.9
Percentage of EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense

us-gaap:EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense


Employee
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value10147.85.47.0136.68.1137.45.77.76.57.611108.512111412159.86.412261616162219172016131312-14.4-11.6-10.010-12.0-14.9-13.0
Percentage of EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EquitySecuritiesFvNiGainLoss

us-gaap:EquitySecuritiesFvNiGainLoss


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value154-436.1734-82.3102-60.92.8-4.6-174.2375-11.81415.4
Percentage of EquitySecuritiesFvNiGainLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EquitySecuritiesFvNiRealizedGainLoss

us-gaap:EquitySecuritiesFvNiRealizedGainLoss


Equity
Period End2021-06-302021-03-312020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0.46.20.00.0-3.2-4.4420.80.10.00.0
Percentage of EquitySecuritiesFvNiRealizedGainLoss100.0100.00.00.0100.0100.0100.0100.0100.00.00.0

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value153-442.3722-82.3102-60.9-0.4-9.0-131.3375-11.71415.40.0
Percentage of EquitySecuritiesFvNiUnrealizedGainLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss dei:LegalEntity

biib:DenaliTherapeuticsInc


Equity
Period End2020-09-30
Value-29.6
Percentage of EquitySecuritiesFvNiUnrealizedGainLoss36.0

biib:IonisPharmaceuticals


Equity
Period End2020-09-302020-06-30
Value6667
Percentage of EquitySecuritiesFvNiUnrealizedGainLoss-80.465.3

biib:IonisSangamoDenaliAndSage


Equity
Period End2021-06-302021-03-31
Value263442
Percentage of EquitySecuritiesFvNiUnrealizedGainLoss170.9-99.9

biib:SangamoCommonStock


Equity
Period End2020-09-302020-06-30
Value1540
Percentage of EquitySecuritiesFvNiUnrealizedGainLoss-18.539.7

us-gaap:EquitySecuritiesFvNiUnrealizedLoss dei:LegalEntity

us-gaap:EquitySecuritiesFvNiUnrealizedLoss

biib:IonisSangamoDenaliAndSage


Equity
Period End2021-06-30
Value105
Percentage of EquitySecuritiesFvNiUnrealizedLoss100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings


Fair
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-0.3336229-10.04.6-2.65720-11.5-79.387-1.95.6-1.5-30.0-21.2-10.04.0-5.9-10.6-2.3-24.613-0.2442.201-7.844-7.3249-4.0190.799-2.4360.0975.163-2.277-3.629-9.456-12.858
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax


Foreign
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-0.8-8.6-5.33.110-18.9-2.3-4.21.7-2.23.90.2-13.0-1.0-2.16.7-2.34.0-7.2-4.90.22.1-13.9-4.3-1.5-13.0-2.1-4.8-1.4-3.3-4.2-3.1-5.3-2.6-2.70.1-1.31.4-0.5-4.8-0.6-0.4-0.3-3.5-0.71.0
Percentage of ForeignCurrencyTransactionGainLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:GainLossOnDerivativeInstrumentsNetPretax us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation

us-gaap:GainLossOnDerivativeInstrumentsNetPretax

us-gaap:ForeignExchangeContract, biib:Cashflowsoperatingexpenses, us-gaap:OperatingExpense


Gain
Period End2021-06-302021-03-312020-06-302020-03-31
Value-0.3-0.1-0.2-0.9
Percentage of GainLossOnDerivativeInstrumentsNetPretax100.0100.0100.0100.0

us-gaap:ForeignExchangeContract, biib:Cashflowsrevenue, us-gaap:Sales


Gain
Period End2021-06-302021-03-312020-06-302020-03-31
Value-0.8-3.0-1.69.3
Percentage of GainLossOnDerivativeInstrumentsNetPretax266.73000.0800.0-1033.3

us-gaap:GainLossOnDerivativeInstrumentsNetPretax us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

us-gaap:InterestRateSwap, us-gaap:InterestExpense


Gain
Period End2021-06-302021-03-312020-12-312020-09-30
Value0.03.30.00.0
Percentage of GainLossOnDerivativeInstrumentsNetPretax-0.0-3300.00.00.0

us-gaap:GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments

us-gaap:GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments


Gain
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value4.817-43.87.88.32.4-8.3100.94.8-2.85.25.25.6-1.21.26.11.6120.4182.4198.1139.74.07.72.41.43.90.20.60.9-1.45.715-4.3106.10.6-4.93.0-10.17.9
Percentage of GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:GoodwillOtherIncreaseDecrease

us-gaap:GoodwillOtherIncreaseDecrease


Goodwill
Period End2021-06-302021-03-312020-12-31
Value800000.01000000.06400000.0
Percentage of GoodwillOtherIncreaseDecrease100.0100.0100.0

us-gaap:ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill biib:Researchanddevelopmentasset, us-gaap:BusinessAcquisition

us-gaap:ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill

biib:BIIB054, biib:Nightstar


Impairment
Period End2020-12-31
Value75
Percentage of ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill100.0

biib:BIIB111, biib:Nightstar


Impairment
Period End2021-06-302020-12-31
Value350115
Percentage of ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill0.0152.5

biib:BIIB112, biib:Nightstar


Impairment
Period End2021-06-30
Value191
Percentage of ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill0.0

us-gaap:ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill biib:Researchanddevelopmentasset, us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass

biib:BIIB111, biib:Nightstar, us-gaap:InProcessResearchAndDevelopment


Impairment
Period End2020-12-31
Value115
Percentage of ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill152.5

us-gaap:IncomeLossFromEquityMethodInvestments

us-gaap:IncomeLossFromEquityMethodInvestments


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value34-18.2-11.41415-14.8-12.6-21.8-16.3-28.70.00.00.00.00.00.00.00.00.00.00.00.00.048-6.833-4.881-0.834-0.194-5.394-1.933-7.605-4.954-6.17-2.289-3.811-2.749-1.258-0.5110.00.00.0
Percentage of IncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.00.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:IncomeLossFromEquityMethodInvestments us-gaap:ProductOrService, us-gaap:TypeOfArrangement

biib:ADUHELM, biib:Eisai


Income
Period End2021-06-30
Value45
Percentage of IncomeLossFromEquityMethodInvestments131.2

us-gaap:IncomeLossFromEquityMethodInvestments us-gaap:TypeOfArrangement

biib:Eisai


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value40330.00.033
Percentage of IncomeLossFromEquityMethodInvestments116.9-185.7-0.00.0223.8

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions

biib:SamsungBiosimilarAgreement


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value3418-7.4131514122116
Percentage of IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccruedIncomeTaxesPayable

us-gaap:IncreaseDecreaseInAccruedIncomeTaxesPayable


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-06-302014-03-31
Value10664-82.8-489.3281223-48.5-242.31361706.1132-74.2257113328580-195.1-85.24.3-376.8225-409.0-103.217-52.015449-18.64
Percentage of IncreaseDecreaseInAccruedIncomeTaxesPayable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccruedLiabilities

us-gaap:IncreaseDecreaseInAccruedLiabilities


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value95-283.6-218.7814-94.0-347.4349107-77.7-138.436487135-121.8277-52.2231-684.2793-60.918-180.8248-4.60335-205.46722549141-171.368173126164-180.9116952134-82.031901081-149.0631134159-82.854
Percentage of IncreaseDecreaseInAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInDueFromRelatedParties

us-gaap:IncreaseDecreaseInDueFromRelatedParties


Increase
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value52-43.886-70.5-78.624300.0
Percentage of IncreaseDecreaseInDueFromRelatedParties100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:IncreaseDecreaseInEquitySecuritiesFvNi

us-gaap:IncreaseDecreaseInEquitySecuritiesFvNi


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value154-437.6723-81.5101-62.0-42.5-9.4-175.8375-12.1137
Percentage of IncreaseDecreaseInEquitySecuritiesFvNi100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

biib:MarketStockUnits


Incremental
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value100000.0100000.00100000.0100000.0100000.00100000.00100000.00100000.0100000.0100000.00100000.0100000.0100000.00200000.0100000.0100000.0-100000.0100000.0100000.0200000.00200000.0200000.0300000.00300000.0300000.0300000.00300000.0200000.0300000.0100000.0200000.0200000.0200000.0
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.0100.00.0100.0100.0100.00.0100.00.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

biib:PerformanceStockUnitsSettledinStock


Incremental
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value100000.0100000.00100000.0100000.0100000.0000000000000
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.0100.00.0100.0100.0100.00.00.00.00.00.00.00.00.00.00.00.00.0

biib:TimeVestedRestrictedStockUnits


Incremental
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value200000.0200000.0100000.0100000.0100000.0100000.0100000.0100000.0100000.0300000.00400000.0100000.0200000.00200000.0100000.0200000.00200000.0100000.0200000.00200000.0200000.0300000.00500000.0400000.0600000.0100000.0700000.0600000.0800000.00900000.0800000.01100000.0-200000.01600000.01400000.01600000.0200000.01500000.01000000.0
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements200.0200.00.0100.0100.0100.00.0100.00.0300.00.0400.0100.0200.00.0200.0100.0200.00.0100.0100.0200.0-0.0200.0200.0150.00.0250.0200.0200.00.0233.3200.0266.70.0300.0400.0366.7-200.0800.0700.0800.00.00.00.0

us-gaap:InvestmentIncomeInterest

us-gaap:InvestmentIncomeInterest


Investment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value2.72.94.06.07.624293029313126282624201616201615119.15.44.33.33.53.62.42.71.51.50.94.36.95.9106.55.95.34.33.73.73.16.78.9
Percentage of InvestmentIncomeInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value-0.5-0.8-3.80.18.7-7.8-2.10.13.36.9-2.1-0.20.6-2.22.61.07.2-1.6-11.6-5.44.52.50.754-2.239-0.2141.299-0.8910.012-6.8651.725-9.7566.2116.077-1.1170.8461.503-0.0831.911-0.316-1.3531.057
Percentage of OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax


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
Value-25.1103-91.2-51.1-4.00.7-2.9197-1.337174.631-24.4-17.9-9.4-16.41.0-14.3-23.4-28.2-26.6-13.2-13.69.623-8.1-8.5-3.71.21.81812-9.0
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment


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
Value0.42.0-33.9-0.50.10.8-3.00.80.10.65.3-0.20.9-0.5-3.60.0-0.60.13.80.40.70.2-10.80.52.81.3-13.30.7-0.20.8-1.10.91.11.2
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-1.61.937.21.0-2.5114.3103.40.4-7.71.629.9-4.32.82.020.1-0.03.710.0-26.6-1.7-2.5-0.881.8-3.729.25.5164.2-8.25.466.7-61.14.88.5-13.3

us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-38.4128-107.0-91.2-27.560-27.793-8.93139-3.4122-60.4-17.3-53.7
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax153.0124.5117.3178.5687.58671.4955.247.3684.683.6220.9-73.9386.4247.596.6571.3

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


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
Value-0.8-1.2-0.50.211-20.80.20.63.97.1-2.7-0.30.6-8.2-9.00.47.1-2.0-11.8-5.44.12.50.5-3.1-0.31.2-1.00.0-0.41.8-2.36.36.21.6
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax3.2-1.20.5-0.4-295.0-2971.4-6.90.3-300.019.0-15.3-6.51.933.650.3-4.3-43.3-200.082.523.1-14.5-9.4-3.822.8-3.15.112.3-0.010.8150.0-127.833.948.1-17.8

us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-2.222-38.8-10.5-5.323-24.92313165.00.00.00.0
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax8.821.742.520.5132.53414.3858.611.8-1069.243.428.20.00.0-0.0

us-gaap:AccumulatedTranslationAdjustment


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
Value15-48.5895016-63.95279-10.3-17.8-29.08.5-92.04412438220-75.8-14.4-58.09.6-35.1-23.563-100.9-38.0-60.2-8.1-2.919338.0-24.4
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-63.3-47.0-97.6-99.6-422.5-9128.6-1810.340.2792.3-47.7-163.8184.8-291.1-183.2-67.0-467.0-504.92000.0530.161.5205.7-36.1265.9172.8657.3-425.7469.1708.2218.9-241.71105.6180.662.0271.1

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax

us-gaap:ForeignExchangeContract, us-gaap:OperatingExpense


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value0.4-0.40.0-0.1
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax100.0100.00.0100.0

us-gaap:ForeignExchangeContract, us-gaap:Sales


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value-30.7-23.12327
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax-7675.05775.00.0-27000.0

us-gaap:OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseBeforeAdjustmentsAndTax us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation

us-gaap:OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseBeforeAdjustmentsAndTax

us-gaap:NetInvestmentHedging, us-gaap:OtherNonoperatingIncomeExpense


Other
Period End2021-03-312020-03-31
Value100000.0900000.0
Percentage of OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseBeforeAdjustmentsAndTax100.0100.0

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value-11.0149-83.7-51.233-65.059-37.916305.2132-29.00.0-35.5-103.0-23.8641.329-47.6-21.416-31.171-96.159873048105.791-7.414-14.847-2.30511-16.064-27.35418-18.36320326.327
Percentage of OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312013-03-31
Value2.5124-73.5-44.5-31.7-14.1-42.9160-33.1207.9134213-12.7
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value-0.4-2.0330.5-0.1-0.83.0-0.8-0.1-0.6-5.30.2-0.90.53.60.00.6-0.1-3.8-0.4-0.7-0.210-0.523-2.851-1.25813-0.6910.17-0.8171.071-0.892-1.011-1.26313-0.198-0.202-0.1899.2850.011-0.004
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncashIncomeExpense

us-gaap:OtherNoncashIncomeExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value-40.7-71.7-21.099999999999984-24.8-39.6-45.7183.7-40.4-50.70.9110-16.3-26.1-35.2-53.4-55.4-18.1-57.8-13.6-40.020-50.636-37.372-27.11332-45.39131-7.26371-8.965-5.9189.05333-25.494-27.113-8.00329-24.721-11.2927.09619
Percentage of OtherNoncashIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForProceedsFromOtherInvestingActivities

us-gaap:PaymentsForProceedsFromOtherInvestingActivities


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value0.7-2.78.918-0.50.5-31.60.65.7-1.70.81.7-1.3-1.65.9-2.20.76.610.0-53.1224326233.3716.7482.8672.3864.7436.002-23.3259.08-4.722110.503152.875198.734294.619-25.995
Percentage of PaymentsForProceedsFromOtherInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsOfFinancingCosts

us-gaap:PaymentsOfFinancingCosts


Payments
Period End2021-06-302021-03-31
Value0.024
Percentage of PaymentsOfFinancingCosts0.0100.0

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation


Payments
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value-12.927-7.4-10.429-6.7-8.632-4.6-7.6-6.921-5.4-7.1-7.725-3.9-9.5-7.729
Percentage of PaymentsRelatedToTaxWithholdingForShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value71391317488952069168412001977125082516011319285519191557
Percentage of PaymentsToAcquireAvailableForSaleSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireInProcessResearchAndDevelopment

us-gaap:PaymentsToAcquireInProcessResearchAndDevelopment


Payments
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.00.00.0750.00.00.00.00.0277510.00.00.01200.00.00.0
Percentage of PaymentsToAcquireInProcessResearchAndDevelopment0.00.00.0100.00.00.00.00.00.0100.0100.0100.00.00.0100.00.00.00.0

us-gaap:PaymentsToAcquireIntangibleAssets

us-gaap:PaymentsToAcquireIntangibleAssets


Payments
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-312014-09-302013-12-312013-09-302012-12-312012-09-30
Value150.00.0371550.00.00.00.00.03.00.065505.18551.2110-28.628-6.30.00.00.00.06.6340.0
Percentage of PaymentsToAcquireIntangibleAssets100.00.00.0100.0100.00.00.00.00.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.00.0

us-gaap:PaymentsToAcquireInterestInSubsidiariesAndAffiliates us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:PaymentsToAcquireInterestInSubsidiariesAndAffiliates

biib:DenaliTherapeuticsInc


Payments
Period End2020-12-31
Value0.0
Percentage of PaymentsToAcquireInterestInSubsidiariesAndAffiliates0.0

biib:SangamoCommonStock


Payments
Period End2020-09-30
Value0.0
Percentage of PaymentsToAcquireInterestInSubsidiariesAndAffiliates0.0

us-gaap:PaymentsToMinorityShareholders

us-gaap:PaymentsToMinorityShareholders


Payments
Period End2020-12-312020-09-302019-12-312019-09-302018-12-312018-09-302017-12-312017-09-302011-12-312011-09-302010-12-312010-09-30
Value-66.3700.00.0-0.5-2.01340.02.9514178.588
Percentage of PaymentsToMinorityShareholders100.0100.00.00.0100.0100.0100.00.0100.0100.0100.0100.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value-31.911-8.33.9144.5-40.222128.7-31.315-6.32.6-18.7-23.42310-40.736-23.524-12.253-77.14226-11.287-2.347-27.339-1.05313-72.688231430-50.2799.773102289-112.711184.3
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities

us-gaap:ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value6338192058136014902389213961117661489117911922733406810938881700188421932362164211816992387601373776625560757164617784329836491599
Percentage of ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesEquity

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesEquity


Proceeds
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value0.0910.00.00.53.31663090.00.00.0
Percentage of ProceedsFromSaleOfAvailableForSaleSecuritiesEquity0.0100.00.00.0100.0100.0100.0100.00.00.00.0

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment


Proceeds
Period End2021-06-302021-03-312019-12-312018-12-31
Value0.0280.00.0
Percentage of ProceedsFromSaleOfPropertyPlantAndEquipment0.0100.00.00.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax


Reclassification
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
Value2721176.6-27.7-14.8-40.0-37.1-31.8-16.7-9.88.7103728182.8-6.3-4.75.34.7-8.7-53.3-42.9-40.1-34.7-13.5-2.7-0.74.2-0.27.20.0-3.7
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedGainLossNetCashFlowHedgeParent


Reclassification
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value2721217.5-23.7-26.9-37.3-34.4-29.0-14.3-8.98.610311718
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax99.398.1120.3113.685.6181.893.292.791.285.690.898.9100.084.059.996.8

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Reclassification
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
Value0.30.4-3.3-0.1-3.113-2.3-0.5-0.6-0.20.60.10.06.0110.60.10.40.20.00.40.00.30.80.10.10.10.1-6.5-0.1-7.5-0.1-0.1-2.7
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax1.11.9-18.6-1.511.2-87.85.81.31.91.2-6.11.10.016.040.13.23.6-6.3-4.30.08.5-0.0-0.6-1.9-0.2-0.3-0.7-3.7928.6-2.43750.0-1.40.073.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossDerivativeQualifyingAsHedgeExcludedComponentIncludingPortionAttributableToNoncontrollingInterest


Reclassification
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-0.3-0.8-0.9-0.9-0.4-2.2-2.2-2.2-1.50.00.00.0
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax-1.7-12.13.26.11.05.96.913.215.30.00.00.0

us-gaap:RepaymentsOfDebt

us-gaap:RepaymentsOfDebt


Repayments
Period End2021-03-312014-03-312013-03-312012-03-31
Value1690.04500.0
Percentage of RepaymentsOfDebt100.00.0100.00.0

us-gaap:RepaymentsOfSeniorDebt

us-gaap:RepaymentsOfSeniorDebt


Repayments
Period End2021-02-28
Value151
Percentage of RepaymentsOfSeniorDebt100.0

us-gaap:RepaymentsOfSeniorDebt us-gaap:DebtInstrument

biib:SeniorNotesFivePointTwoPercentDueTwentyFortyFive


Repayments
Period End2021-02-28
Value12
Percentage of RepaymentsOfSeniorDebt8.0

us-gaap:ResearchAndDevelopmentInProcess

us-gaap:ResearchAndDevelopmentInProcess


Research
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value180.00.00.0750.00.00.00.00.0277510.00.00.01200.00.00.00.0
Percentage of ResearchAndDevelopmentInProcess100.00.00.00.0100.00.00.00.00.00.0100.0100.0100.00.00.0100.00.00.00.00.0

us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised

us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0300000.0100000.000300000.00100000.00300000.0000300000.0
Percentage of StockIssuedDuringPeriodSharesStockOptionsExercised0.0100.0100.00.00.0100.00.0100.00.0100.00.00.00.0100.0

us-gaap:StockIssuedDuringPeriodSharesTreasuryStockReissued us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesTreasuryStockReissued

us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value100000.0100000.00100000.00100000.00100000.00100000.0100000.000100000.0
Percentage of StockIssuedDuringPeriodSharesTreasuryStockReissued100.0100.00.0100.00.0100.00.0100.00.0100.0100.00.00.0100.0

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-0.8-46.8-3.4-2.3-0.3-47.83.10.71.1483.91.11.537
Percentage of StockIssuedDuringPeriodValueStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised us-gaap:StatementEquityComponents

us-gaap:Parent


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-0.8-46.8-3.4-2.3-0.3-47.8-3.1-0.7-1.1-48.9
Percentage of StockIssuedDuringPeriodValueStockOptionsExercised100.0100.0100.0100.0100.0100.0-100.0-100.0-100.0-100.0

us-gaap:RetainedEarnings


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-0.8-46.8-3.4-2.3-0.347-104.50.71.148
Percentage of StockIssuedDuringPeriodValueStockOptionsExercised100.0100.0100.0100.0100.0-100.0-3371.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueTreasuryStockReissued

us-gaap:StockIssuedDuringPeriodValueTreasuryStockReissued


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1319109.711187.37.39.6167.98.78.416
Percentage of StockIssuedDuringPeriodValueTreasuryStockReissued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueTreasuryStockReissued us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1319109.711187.37.39.6167.98.78.416
Percentage of StockIssuedDuringPeriodValueTreasuryStockReissued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1319109.711187.37.39.616
Percentage of StockIssuedDuringPeriodValueTreasuryStockReissued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockRepurchasedAndRetiredDuringPeriodShares us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents

us-gaap:StockRepurchasedAndRetiredDuringPeriodShares

biib:December2019ShareRepurchaseProgram, us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value1.62.24.59.03.2
Percentage of StockRepurchasedAndRetiredDuringPeriodShares100.0100.0100.0100.0100.0

biib:December2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Stock
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value1.62.24.59.03.2
Percentage of StockRepurchasedAndRetiredDuringPeriodShares100.0100.0100.0100.0100.0

biib:March2019ShareRepurchaseProgram, us-gaap:CommonStock


Stock
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value-4.656612873077392e-160.04.17.73.13.9
Percentage of StockRepurchasedAndRetiredDuringPeriodShares-0.00.0128.10.00.00.0

biib:March2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Stock
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value-4.656612873077392e-160.04.17.73.13.9
Percentage of StockRepurchasedAndRetiredDuringPeriodShares-0.00.0128.10.00.00.0

us-gaap:StockholdersEquityOther

us-gaap:StockholdersEquityOther


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312018-12-312018-09-302018-06-302018-03-31
Value0.0-1.50.00.00.00.6-373.80.00.0479
Percentage of StockholdersEquityOther0.0100.00.00.00.0100.0100.00.00.0100.0

us-gaap:StockholdersEquityOther us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value0.0-1.50.00.00.00.6
Percentage of StockholdersEquityOther0.0100.00.00.00.0100.0

us-gaap:Parent


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value0.0-1.50.00.00.00.6
Percentage of StockholdersEquityOther0.0100.00.00.00.0100.0

us-gaap:TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense

us-gaap:TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense


Tax
Period End2020-09-302020-06-302020-03-31
Value0.0-62.0697
Percentage of TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense0.0100.0100.0

us-gaap:TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease

us-gaap:TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease


Translation
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-2.322-11.3-6.2232111140.00.00.0
Percentage of TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship

us-gaap:NetInvestmentHedging


Translation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-2.523-40.1-10.4-8.824-20.1221111-3.80.00.00.0
Percentage of TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease108.7106.20.092.0141.9105.20.0103.899.184.30.00.00.00.0

us-gaap:TreasuryStockRetiredCostMethodAmount us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents

us-gaap:TreasuryStockRetiredCostMethodAmount

biib:December2019ShareRepurchaseProgram, us-gaap:AdditionalPaidInCapital


Treasury
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value6993456015
Percentage of TreasuryStockRetiredCostMethodAmount100.0100.0100.0100.0100.0

biib:December2019ShareRepurchaseProgram, us-gaap:RetainedEarnings


Treasury
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value38050612042748925
Percentage of TreasuryStockRetiredCostMethodAmount547.5539.72671.64527.55932.7

biib:December2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Treasury
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value-450.0-600.0-1250.0-2808.9-941.1
Percentage of TreasuryStockRetiredCostMethodAmount-647.5-639.7-2771.6-4627.5-6032.7

biib:March2019ShareRepurchaseProgram, us-gaap:AdditionalPaidInCapital


Treasury
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value0.00.071465519
Percentage of TreasuryStockRetiredCostMethodAmount0.00.0455.10.00.00.0

biib:March2019ShareRepurchaseProgram, us-gaap:RetainedEarnings


Treasury
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value0.00.012082046662890
Percentage of TreasuryStockRetiredCostMethodAmount0.00.07744.20.00.00.0

biib:March2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Treasury
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value0.00.0-1279.15348-717.9-909.9
Percentage of TreasuryStockRetiredCostMethodAmount0.00.0-8199.40.00.00.0

us-gaap:TreasuryStockSharesAcquired us-gaap:ShareRepurchaseProgram

us-gaap:TreasuryStockSharesAcquired

biib:December2019ShareRepurchaseProgram


Treasury
Period End2021-06-302020-09-302020-06-302020-03-31
Value9.04.59.03.2
Percentage of TreasuryStockSharesAcquired100.0100.0100.0100.0

biib:March2019ShareRepurchaseProgram


Treasury
Period End2020-09-302020-06-302020-03-31
Value-4.656612873077392e-164.14.1
Percentage of TreasuryStockSharesAcquired-0.045.6128.1

biib:October2020ShareRepurchaseProgram


Treasury
Period End2021-06-302021-03-31
Value1.62.2
Percentage of TreasuryStockSharesAcquired17.80.0

us-gaap:TreasuryStockSharesAcquired us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents

biib:December2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Treasury
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value1.62.24.59.03.2
Percentage of TreasuryStockSharesAcquired17.80.0100.0100.0100.0

biib:March2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Treasury
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value-4.656612873077392e-160.04.17.73.13.9
Percentage of TreasuryStockSharesAcquired-0.00.0128.10.00.00.0

us-gaap:TreasuryStockSharesAcquired us-gaap:StatementEquityComponents

us-gaap:CommonStock


Treasury
Period End2020-09-30
Value-4.5
Percentage of TreasuryStockSharesAcquired-100.0

us-gaap:TreasuryStockValueAcquiredCostMethod us-gaap:ShareRepurchaseProgram

us-gaap:TreasuryStockValueAcquiredCostMethod

biib:December2019ShareRepurchaseProgram


Treasury
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value45060012502808941
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.0100.0100.0

biib:March2019ShareRepurchaseProgram


Treasury
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value0.00.012792093717909
Percentage of TreasuryStockValueAcquiredCostMethod0.00.0135.90.00.00.0

us-gaap:TreasuryStockValueAcquiredCostMethod us-gaap:ShareRepurchaseProgram, us-gaap:StatementEquityComponents

biib:December2019ShareRepurchaseProgram, us-gaap:Parent


Treasury
Period End2021-06-302021-03-312020-09-302020-06-30
Value45060012502808
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.0100.0

biib:December2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Treasury
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value45060012502808941
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.0100.0100.0

biib:March2019ShareRepurchaseProgram, us-gaap:Parent


Treasury
Period End2020-09-302020-06-302020-03-312019-09-302019-06-30
Value0.00.01279717909
Percentage of TreasuryStockValueAcquiredCostMethod0.00.0135.90.00.0

biib:March2019ShareRepurchaseProgram, us-gaap:TreasuryStock


Treasury
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value0.00.012792093717909
Percentage of TreasuryStockValueAcquiredCostMethod0.00.0135.90.00.00.0

us-gaap:UnrealizedGainLossOnForeignCurrencyDerivativesNetBeforeTax us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship

us-gaap:UnrealizedGainLossOnForeignCurrencyDerivativesNetBeforeTax

us-gaap:NetInvestmentHedging


Unrealized
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-2.62.717-10.4-8.822-40.122118.0
Percentage of UnrealizedGainLossOnForeignCurrencyDerivativesNetBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:UnrealizedGainLossOnInvestments

us-gaap:UnrealizedGainLossOnInvestments


Unrealized
Period End2020-09-302019-09-30
Value-82.140
Percentage of UnrealizedGainLossOnInvestments100.0100.0

us-gaap:WeightedAverageNumberDilutedSharesOutstandingAdjustment

us-gaap:WeightedAverageNumberDilutedSharesOutstandingAdjustment


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value400000.0400000.0300000.0300000.0300000.0200000.0100000.0400000.0500000.0200000.0300000.0400000.0300000.0300000.0500000.0300000.0400000.0400000.0400000.0600000.0800000.0700000.01000000.01200000.01200000.01500000.01600000.01600000.02000000.02500000.02600000.03000000.02400000.01800000.02800000.0
Percentage of WeightedAverageNumberDilutedSharesOutstandingAdjustment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:AccruedExpensesOnFundingCommitmentRelatedToClinicalResearch

biib:AccruedExpensesOnFundingCommitmentRelatedToClinicalResearch


Accrued
Period End2020-12-31
Value21
Percentage of AccruedExpensesOnFundingCommitmentRelatedToClinicalResearch100.0

biib:AdditionalMilestonePayment us-gaap:ProductOrService, us-gaap:TypeOfArrangement

biib:AdditionalMilestonePayment

biib:ADUHELM, biib:Eisai


Additional
Period End2021-06-302020-06-30
Value10075
Percentage of AdditionalMilestonePayment100.0100.0

biib:AdditionalMilestonePayment us-gaap:TypeOfArrangement

biib:Eisai


Additional
Period End2021-03-312020-06-302018-12-312017-12-312016-12-312015-12-312014-12-312014-03-31
Value75756256251000100010001000
Percentage of AdditionalMilestonePayment0.0100.00.00.00.00.00.00.0

biib:AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsAmortizedCost

biib:AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsAmortizedCost


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value444049107601231731211071351431339777327269255263277281221163185127147125126109796252213.20.029221120819116515214211078207
Percentage of AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsAmortizedCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsFairValue

biib:AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsFairValue


Available
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value444049107591231731221071341431339677327269255263276281221162184127147125126109796252213.20.029221120719116515214211079210
Percentage of AvailableForSaleSecuritiesDebtMaturitiesAfterFiveYearsFairValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Collaborationexpensesaccrual

biib:Collaborationexpensesaccrual


Collaborationexpensesaccrual
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value3833903892771721542811881302162611011561761831801888913031
Percentage of Collaborationexpensesaccrual100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:Collaborationexpensesaccrual us-gaap:BalanceSheetLocation

us-gaap:OtherCurrentLiabilities


Collaborationexpensesaccrualus-gaap:
Period End2020-12-312019-12-31
Value389281
Percentage of Collaborationexpensesaccrual100.0100.0

biib:ComputerSoftwareAndHardware

biib:ComputerSoftwareAndHardware


Computer
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312012-09-302011-12-312010-12-312009-12-31
Value903798798767746647547559476465439392334
Percentage of ComputerSoftwareAndHardware100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:DeferredTaxAssetsValueReductionInValue us-gaap:ProductOrService

biib:DeferredTaxAssetsValueReductionInValue

biib:TECFIDERA


Deferred
Period End2020-12-31
Value1700
Percentage of DeferredTaxAssetsValueReductionInValue100.0

biib:DeferredTaxAssetsValueReductioninValue us-gaap:ProductOrService

biib:DeferredTaxAssetsValueReductioninValue

biib:TECFIDERA


Deferred
Period End2021-06-302021-03-312020-09-30
Value170017001627
Percentage of DeferredTaxAssetsValueReductioninValue100.0100.0100.0

biib:DeferredTaxLiabilitiesDepreciationAmortizationOther

biib:DeferredTaxLiabilitiesDepreciationAmortizationOther


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value227135102107113102105112146133114115
Percentage of DeferredTaxLiabilitiesDepreciationAmortizationOther100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

biib:DeferredTaxLiabilitiesTaxCreditCarryforwards

biib:DeferredTaxLiabilitiesTaxCreditCarryforwards


Deferred
Period End2020-12-312019-12-312018-12-312017-12-31
Value-174600000.0-1617200000.0-1425700000.00
Percentage of DeferredTaxLiabilitiesTaxCreditCarryforwards100.0100.0100.00.0

biib:DeferredTaxLiabilitiesValueReductionInValue us-gaap:ProductOrService

biib:DeferredTaxLiabilitiesValueReductionInValue

biib:TECFIDERA


Deferred
Period End2020-12-31
Value1600
Percentage of DeferredTaxLiabilitiesValueReductionInValue100.0

biib:DeferredTaxLiabilitiesValueReductioninValue us-gaap:ProductOrService

biib:DeferredTaxLiabilitiesValueReductioninValue

biib:TECFIDERA


Deferred
Period End2021-06-302021-03-312020-09-30
Value160016001538
Percentage of DeferredTaxLiabilitiesValueReductioninValue100.0100.0100.0

biib:DeferredtaxliabilitiesGILTItaxcalculation

biib:DeferredtaxliabilitiesGILTItaxcalculation


Deferredtaxliabilities
Period End2020-12-312019-12-312018-12-312017-12-31
Value-1143.7-1381.6-544.60.0