XML 112 R93.htm IDEA: XBRL DOCUMENT
v3.24.1.u1

Collaborative and Other Relationships - ADUHELM Collaboration Agreement (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2024 | Mar. 31, 2023 | Dec. 31, 2023
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Excess and obsolescence charges related to inventory | $ 27.5 | $ 17.4 |
Eisai |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Amounts receivable | 15.9 |  | $ 1.4
Amounts payable | $ 180.7 |  | $ 118.4

X
- Definition Accounts Payable, To Collaborator + References No definition available. + Details
Name: | biib_AccountsPayableToCollaborator
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Accounts Receivable, From Collaborator + References No definition available. + Details
Name: | biib_AccountsReceivableFromCollaborator
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 808 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479402/808-10-50-1 + Details
Name: | us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 330 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483080/330-10-50-2 + Details
Name: | us-gaap_InventoryWriteDown
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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