XML 116 R84.htm IDEA: XBRL DOCUMENT
v3.22.2.2

Dispositions (Details Textual) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Apr. 30, 2022 USD ($) | Sep. 30, 2022 USD ($) | Sep. 30, 2022 USD ($) | Sep. 30, 2021 USD ($) | Jan. 31, 2022 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Gain on sale of equity interest in Samsung Bioepis |  |  | $ (1,505.4) | $ 0.0 |
Samsung Bioepis |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Equity, ownership interest |  | 49.90% | 49.90% |  |
Samsung Bioepis | Fair Value, Recurring |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Other current assets, receivable |  | $ 790.8 | $ 790.8 |  |
Other assets, receivable |  | $ 402.8 | $ 402.8 |  |
Samsung Bioepis | Payment Due At First Anniversary | Discount rate | Fair Value, Recurring |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Risk-adjusted discount rates |  | 0.049 | 0.049 |  |
Samsung Bioepis | Payment Due At Second Anniversary | Discount rate | Fair Value, Recurring |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Risk-adjusted discount rates |  | 0.053 | 0.053 |  |
Samsung Bioepis |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Proceeds from divestiture of interest in joint venture | $ 1,000.0 |  |  |  |
Payables to divestiture of interest in joint venture |  |  |  |  | $ 1,300.0
Gain on sale of equity interest in Samsung Bioepis |  |  | $ 1,500.0 |  |
Cumulative translation loss |  |  | 58.9 |  |
Gain on derivative used in net investment hedge |  |  | 57.0 |  |
Gain (loss) on sale |  | $ 2.7 | (4.0) |  |
Additional milestone payment | $ 50.0 |  |  |  |
Contingent discount on common shares | 5.00% |  |  |  |
Discrete income tax expense (benefit) |  | $ 258.3 | $ 258.3 |  |
Samsung Bioepis | Payment Due At First Anniversary |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Payables to divestiture of interest in joint venture |  |  |  |  | 812.5
Samsung Bioepis | Payment Due At Second Anniversary |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Payables to divestiture of interest in joint venture |  |  |  |  | $ 437.5

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 Discrete Income Tax Expense (Benefit) + References No definition available. + Details
Name: | biib_DiscreteIncomeTaxExpenseBenefit
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Other Assets, Current, Fair Value Disclosure, + References No definition available. + Details
Name: | biib_OtherAssetsCurrentFairValueDisclosure
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Other Assets, Measurement Input + References No definition available. + Details
Name: | biib_OtherAssetsMeasurementInput
Namespace Prefix: | biib_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Payables To Divestiture Of Interest In Joint Venture + References No definition available. + Details
Name: | biib_PayablesToDivestitureOfInterestInJointVenture
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Payables To Divestiture Of Interest In Joint Venture, Contingent Discount on Shares, Percent + References No definition available. + Details
Name: | biib_PayablesToDivestitureOfInterestInJointVentureContingentDiscountOnSharesPercent
Namespace Prefix: | biib_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 + Details
Name: | us-gaap_GainLossOnDispositionOfAssets1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities. + References Reference 1: 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=123570139&loc=d3e3602-108585 + Details
Name: | us-gaap_GainLossOnSaleOfInvestments
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_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of other assets. + References No definition available. + Details
Name: | us-gaap_OtherAssetsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before tax, after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669646-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, before tax, of reclassification from accumulated other comprehensive income (AOCI) for gain (loss) from derivative designated and qualifying as net investment hedge. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CCC -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109998896-113959 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The cash inflow from the sale of an investment interest in a joint venture that the reporting entity has not previously accounted for using consolidation or the equity method of accounting. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3179-108585 + Details
Name: | us-gaap_ProceedsFromDivestitureOfInterestInJointVenture
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=biib_SamsungBiosimilarAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | biib_FutureContingentMilestoneTypesAxis=biib_PaymentDueAtFirstAnniversaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | biib_FutureContingentMilestoneTypesAxis=biib_PaymentDueAtSecondAnniversaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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