2.2.0.7 true Property, Plant and Equipment (Details) (USD $) 0609 - Disclosure - Property, Plant and Equipment (Details) true false false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ false 2 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ false 3 USD true false false false biib_SanDiegoFacilityMember biib_FacilityLocationAxis xbrldi http://xbrl.org/2006/xbrldi biib_SanDiegoFacilityMember biib_FacilityLocationAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 4 USD true false false false biib_SanDiegoFacilityMember biib_FacilityLocationAxis xbrldi http://xbrl.org/2006/xbrldi biib_SanDiegoFacilityMember biib_FacilityLocationAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ 5 3 us-gaap_PropertyPlantAndEquipmentNetAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false xbrli:stringItemType string No definition available. false 6 4 us-gaap_PropertyPlantAndEquipmentNet us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 true true false false 1641791000 1641791000 false false false 2 true true false false 1637083000 1637083000 false false false 3 false false false false 0 0 true false false 4 true true false false 128400000 128400000 true false false xbrli:monetaryItemType monetary Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, and production equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph a -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 12 -Paragraph 5 -Subparagraph b, c Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 7 false 7 3 biib_AccumulatedDepreciationOfPropertyPlantAndEquipmentTextualsAbstract biib false na duration Accumulated Depreciation Of Property Plant And Equipment. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false xbrli:stringItemType string Accumulated Depreciation Of Property Plant And Equipment. false 8 4 us-gaap_SaleLeasebackTransactionGrossProceeds us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 128000000 128000000 true false false 4 false false false false 0 0 true false false xbrli:monetaryItemType monetary The gross proceeds received from the asset(s) sold in connection with the transaction involving the sale of property to another party and the lease back to the seller. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 98 -Section Appendix A -Paragraph 28, 29 false 9 4 biib_AcresOfLand biib false na duration Acres Of Land. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 43 43 true false false xbrli:integerItemType integer Acres Of Land. No authoritative reference available. false 10 4 biib_SquareFeetOfLaboratoryAndOfficeSpace biib false na duration Square feet of Laboratory And Office Space. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 355000 355000 true false false xbrli:integerItemType integer Square feet of Laboratory And Office Space. No authoritative reference available. false 11 4 biib_SquareFootageToBeLeasedIfExerciseOptionToLeaseBuildToSuitProperty biib false na duration Square footage to be leased, if exercise option to lease build to suit property. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 160000 160000 true false false xbrli:integerItemType integer Square footage to be leased, if exercise option to lease build to suit property. No authoritative reference available. false 12 4 biib_SaleLeasebackTransactionPeriodInMonths biib false na duration Sale - Leaseback transaction period In months. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 15 15 true false false xbrli:integerItemType integer Sale - Leaseback transaction period In months. No authoritative reference available. false 13 4 biib_LeaseTermAssociatedWithOptionToLeaseBuildToSuitProperty biib false na duration Lease term associated with option to lease build to suit property. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 10 10 true false false xbrli:integerItemType integer Lease term associated with option to lease build to suit property. No authoritative reference available. false 14 4 biib_TotalDebtServiceAndInterestPaymentsSaleLeasebackTransaction biib false debit instant Total Debt service and interest payments, Sale Leaseback Transaction. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 9400000 9400000 true false false xbrli:monetaryItemType monetary Total Debt service and interest payments, Sale Leaseback Transaction. No authoritative reference available. false 15 4 biib_AmountHeldInEscrowByBuyerToBeReceivedInExchangeForExercisingOptionToLeaseBuildToSuitProperty biib false debit duration Amount held in escrow by buyer, to be received in exchange for exercising option to lease build to suit property. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 22000000 22000000 true false false xbrli:monetaryItemType monetary Amount held in escrow by buyer, to be received in exchange for exercising option to lease build to suit property. No authoritative reference available. false 16 1 us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 true true false false 737700000 737700000 false false false 2 true true false false 642500000 642500000 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false xbrli:monetaryItemType monetary The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -Subparagraph c Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 14 -Article 5 false 4 12 false NoRounding UnKnown UnKnown false true