XML 116 R94.htm IDEA: XBRL DOCUMENT
v3.24.3

Collaborative and Other Relationships - Summary of Activity Related to BAN2401 and Elenbecestat Collaboration (Details) - E2609 and BAN2401 - Eisai - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |
Total development expense incurred by the collaboration related to the advancement of LEQEMBI | $ 77.7 | $ 88.5 | $ 255.6 | $ 282.6
Expense reflected within statements of income | 38.8 | 44.3 | 127.8 | 141.3
Selling, general and administrative |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |
Expense reflected within statements of income | 82.3 | 81.7 | 238.1 | 95.5
Expense incurred by the collaboration | $ 164.6 | $ 163.4 | $ 476.2 | $ 191.0

X
- Definition Total expense incurred by collaboration. + References No definition available. + Details
Name: | biib_ExpenseIncurredByCollaboration
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Expense incurred by the collaboration + References No definition available. + Details
Name: | biib_Expenseincurredbythecollaboration
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Expense reflected within statements of income + References No definition available. + Details
Name: | biib_Expensereflectedwithinstatementsofincome
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 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
- Details
Name: | srt_ProductOrServiceAxis=biib_E2609andBAN2401Member
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_IncomeStatementLocationAxis=us-gaap_SellingGeneralAndAdministrativeExpensesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |