XML 107 R83.htm IDEA: XBRL DOCUMENT
v3.25.2

Leases - Narrative (Details) $ in Millions | 1 Months Ended
--- | ---
Mar. 31, 2025 USD ($) ft² product
Lessee, Lease, Description [Line Items] |
Operating lease area | ft² | 580,000
Reduction of real estate footprint | 40.00%
Term of contract | 15 years 6 months
Estimated minimum lease payments | $ | $ 1,500.0
Headquarters Lease, Five Year Renewal Option | Building |
Lessee, Lease, Description [Line Items] |
Number of renewal options | 3
Renewal term | 5 years
Headquarters Lease, Six Month Renewal Option | Building |
Lessee, Lease, Description [Line Items] |
Number of renewal options | 1
Renewal term | 6 months

X
- Definition Lessee, Operating Lease, Number Of Renewal Options + References No definition available. + Details
Name: | biib_LesseeOperatingLeaseNumberOfRenewalOptions
Namespace Prefix: | biib_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Operating Lease Area + References No definition available. + Details
Name: | biib_OperatingLeaseArea
Namespace Prefix: | biib_
Data Type: | dtr-types:areaItemType
Balance Type: | na
Period Type: | instant

X
- Definition Reduction Of Real Estate Footprint + References No definition available. + Details
Name: | biib_ReductionOfRealEstateFootprint
Namespace Prefix: | biib_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-3 + Details
Name: | us-gaap_LesseeLeaseDescriptionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Term of lessee's operating lease not yet commenced, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-3 + Details
Name: | us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-3 + Details
Name: | us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of unrecorded obligation to transfer funds in future for fixed or minimum amount or quantity of product and service at fixed or minimum price. Includes, but is not limited to, lease not yet commenced and take-or-pay and throughput contracts. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 440 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482648/440-10-50-4 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-3 + Details
Name: | us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_LeaseContractualTermAxis=biib_HeadquartersLeaseFiveYearRenewalOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LeaseContractualTermAxis=biib_HeadquartersLeaseSixMonthRenewalOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |