XML 193 R139.htm IDEA: XBRL DOCUMENT v3.20.4

Investments in Variable Interest Entities (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended			24 Months Ended
	May 31, 2018	Oct. 31, 2017	Jun. 30, 2020	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Variable Interest Entity [Line Items]
Payment to Neurimmune					$ 4.6	$ 0.0	$ 0.0
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our consolidated statements of income					3.3	(77.4)	0.0
Potential future milestone payments commitment to third party approximately					10,200.0			$ 10,200.0
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities					12.8	22.7		12.8
Twelve months
Variable Interest Entity [Line Items]
Potential future milestone payments commitment to third party approximately					$ 200.0			200.0
Neurimmune
Variable Interest Entity [Line Items]
Term of collaboration agreement					12 years
Research and development costs, percentage					100.00%
Payment to Neurimmune	$ 50.0	$ 150.0
Reduction in royalty rate payable on commercial sales		15.00%
Additional reduction in royalty rate payable on commercial sales	5.00%
Regulatory Milestones
Variable Interest Entity [Line Items]
Potential future milestone payments commitment to third party approximately					$ 1,300.0			$ 1,300.0
Eisai
Variable Interest Entity [Line Items]
Total aducanumab collaboration third party milestone expense			$ 75.0		75.0	0.0	0.0
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our consolidated statements of income					$ 33.8	$ 0.0	$ 0.0
Percentage of future development costs related to Eisai				15.00%	45.00%			45.00%
Neurimmune | Regulatory Milestones
Variable Interest Entity [Line Items]
Potential future milestone payments commitment to third party approximately					$ 100.0			$ 100.0
Aducanumab | Regulatory Milestones | European Union
Variable Interest Entity [Line Items]
Potential future milestone payments commitment to third party approximately					50.0			50.0
Aducanumab | Regulatory Milestones | JAPAN
Variable Interest Entity [Line Items]
Potential future milestone payments commitment to third party approximately					$ 50.0			$ 50.0

X

- Definition

Additional milestone payment.

+ References

No definition available.

+ Details

Name:	biib_AdditionalMilestonePayment
Namespace Prefix:	biib_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Additional reduction in royalty rate payable on commercial sales

+ References

No definition available.

+ Details

Name:	biib_Additionalreductioninroyaltyratepayableoncommercialsales
Namespace Prefix:	biib_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Investment in biotechnology companies that are determined to be unconsolidated variable interest entities.

+ References

No definition available.

+ Details

Name:	biib_InvestmentInBiotechnologyCompaniesThatAreDeterminedToBeUnconsolidatedVariableInterestEntities
Namespace Prefix:	biib_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Percentage of future development costs related to Eisai

+ References

No definition available.

+ Details

Name:	biib_PercentageoffuturedevelopmentcostsrelatedtoEisai
Namespace Prefix:	biib_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Potential future milestone payments commitment to third party approximately.

+ References

No definition available.

+ Details

Name:	biib_PotentialFutureMilestonePaymentsCommitmentToThirdPartyApproximately
Namespace Prefix:	biib_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Reduction in royalty rate payable on commercial sales

+ References

No definition available.

+ Details

Name:	biib_Reductioninroyaltyratepayableoncommercialsales
Namespace Prefix:	biib_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Research and Development Costs, Percentage

+ References

No definition available.

+ Details

Name:	biib_ResearchAndDevelopmentCostsPercentage
Namespace Prefix:	biib_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Term of collaboration agreement

+ References

No definition available.

+ Details

Name:	biib_Termofcollaborationagreement
Namespace Prefix:	biib_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of income (loss) for proportionate share of equity method investee's income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(12))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(10))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(13)(f))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109237563&loc=d3e33749-111570

+ Details

Name:	us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of cash outflow to a noncontrolling interest. Includes, but not limited to, reduction of noncontrolling interest ownership. Excludes dividends paid to the noncontrolling interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsToMinorityShareholders
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_VariableInterestEntityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	biib_ExpectedPaymentTimelineofMilestoneAxis=biib_TwelvemonthsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ConsolidatedEntitiesAxis=biib_NeurimmuneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	biib_FutureContingentMilestoneTypesAxis=biib_RegulatoryMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_TypeOfArrangementAxis=biib_EisaiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_TypeOfArrangementAxis=biib_NeurimmuneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_TypeOfArrangementAxis=biib_AducanumabMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementGeographicalAxis=us-gaap_EuropeanUnionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementGeographicalAxis=country_JP
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: