XML 95 R70.htm IDEA: XBRL DOCUMENT
v3.23.1

Share-Based Payments (Details 1) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2023 | Mar. 31, 2022
Summary of share based compensation expense associated with different programs [Abstract] |  |
Share-based compensation expense | $ (78.9) | $ (70.4)
Subtotal | 81.4 | 71.8
Capitalized share-based compensation costs | (3.3) | (2.8)
Share-based compensation expense included in total costs and expenses | 78.1 | 69.0
Market stock units |  |
Summary of share based compensation expense associated with different programs [Abstract] |  |
Share-based compensation expense | 2.2 | 5.9
Time-vested restricted stock units |  |
Summary of share based compensation expense associated with different programs [Abstract] |  |
Share-based compensation expense | 61.7 | 51.3
Performance stock units settled in stock |  |
Summary of share based compensation expense associated with different programs [Abstract] |  |
Share-based compensation expense | 9.5 | 8.3
Performance stock units settled in cash |  |
Summary of share based compensation expense associated with different programs [Abstract] |  |
Share-based compensation expense | 2.5 | 1.4
Employee stock purchase plan |  |
Summary of share based compensation expense associated with different programs [Abstract] |  |
Share-based compensation expense | 4.7 | 4.9
Options | Nightstar |  |
Summary of share based compensation expense associated with different programs [Abstract] |  |
Fair value of post-combination equity compensation | $ 0.8 | $ 0.0

X
- Definition Share based compensation expense included in costs and expenses. + References No definition available. + Details
Name: | biib_ShareBasedCompensationExpenseIncludedInCostsAndExpenses
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Summary of share-based compensation expense associated with different programs. + References No definition available. + Details
Name: | biib_SummaryOfShareBasedCompensationExpenseAssociatedWithDifferentProgramsAbstract
Namespace Prefix: | biib_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, after tax, of expense for award under share-based payment arrangement. + References No definition available. + Details
Name: | us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The expenses and losses recorded for each transaction with the acquiree that was recognized separately from the acquisition of assets and assumptions of liabilities in the business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(3) -URI https://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
Name: | us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsExpensesAndLossesRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of cost capitalized for award under share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(ii) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_MarketStockUnitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_TimeVestedRestrictedStockUnitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_PerformanceStockUnitsSettledinStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_PerformanceStockUnitsSettledinCashMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_EmployeeStockPurchasePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=biib_NightstarMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |