XML 88 R63.htm IDEA: XBRL DOCUMENT
v3.23.1

Derivative Instruments (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2023 | Mar. 31, 2022 | Dec. 31, 2022 | May 31, 2018
Derivatives [Line Items] |  |  |  |
Gain (loss) on foreign currency derivative instruments not designated as hedging instruments | $ (1.8) | $ (12.2) |  |
Gains (losses) on net investment hedges, net of tax | $ 0.0 | 6.2 |  |
Minimum |  |  |  |
Derivatives [Line Items] |  |  |  |
Range of durations of foreign currency forward contracts | 1 month |  | 1 month |
Maximum |  |  |  |
Derivatives [Line Items] |  |  |  |
Range of durations of foreign currency forward contracts | 18 months |  | 12 months |
Not designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative, Notional Amount | $ 1,436.3 |  | $ 1,238.8 |
Other current assets | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative asset, fair value | 12.3 |  | 37.9 |
Other current assets | Not designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative asset, fair value | 22.7 |  | 25.1 |
Other noncurrent assets | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative asset, fair value | 0.1 |  | 0.0 |
Accrued expenses and other | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative liability, fair value | 31.9 |  | 18.4 |
Accrued expenses and other | Not designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative liability, fair value | 7.6 |  | 7.6 |
Foreign exchange contract | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative, Notional Amount | 2,270.6 |  | 1,715.5 |
Foreign Exchange Forward |  |  |  |
Derivatives [Line Items] |  |  |  |
Unrealized Gain on Derivatives | 8.8 | 29.9 |  |
Unrealized Loss on Derivatives | (39.0) | (21.3) |  |
Unrealized Gain (Loss) on Derivatives | (30.2) | 8.6 |  |
Net Investment Hedging |  |  |  |
Derivatives [Line Items] |  |  |  |
Gains (losses) on net investment hedges, net of tax |  | 10.1 |  |
Gains (losses) on net investment hedge, excluded component |  | (3.3) |  |
Cash Flow Hedging [Member] | Foreign exchange contract | Other long-term liabilities |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative liability, fair value | 0.3 |  | 0.0 |
Revenue | Foreign exchange contract |  |  |  |
Derivatives [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax | 17.6 | 20.9 |  |
Revenue | Cash flows, revenue | Foreign exchange contract |  |  |  |
Derivatives [Line Items] |  |  |  |
Gain on interest rate swap | 1.6 | (6.5) |  |
Operating expense | Foreign exchange contract |  |  |  |
Derivatives [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax | (0.5) | (0.3) |  |
Operating expense | Cash flows, operating expenses | Foreign exchange contract |  |  |  |
Derivatives [Line Items] |  |  |  |
Gain on interest rate swap | (2.1) | (0.1) |  |
Other income (expense) | Net Investment Hedging |  |  |  |
Derivatives [Line Items] |  |  |  |
Gain (loss) recognized in net income, excluded component |  | $ (1.1) |  |
Euro | Foreign exchange contract | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative, Notional Amount | 1,854.8 |  | 1,495.5 |
Swiss franc | Foreign exchange contract | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative, Notional Amount | 124.3 |  | 162.8 |
Japan, Yen | Foreign exchange contract | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative, Notional Amount | 43.3 |  | 57.2 |
Canadian dollar | Foreign exchange contract | Designated as hedging instrument |  |  |  |
Derivatives [Line Items] |  |  |  |
Derivative, Notional Amount | $ 248.2 |  | $ 0.0 |
Samsung Bioepis |  |  |  |
Derivatives [Line Items] |  |  |  |
Equity, ownership interest | 49.90% | 49.90% |  |
Percentage of stake in entity |  |  |  | 5.00%
Short-term derivative |  |  |  |
Derivatives [Line Items] |  |  |  |
Range of durations of foreign currency forward contracts | 12 months |  |  |
Gain/Loss on fair value of foreign currency forward contracts | $ 30.0 |  |  |

X
- Definition Derivatives used in net investment hedge, net of tax, excluded component increase (decrease) + References No definition available. + Details
Name: | biib_Derivativesusedinnetinvestmenthedgenetoftaxexcludedcomponentincreasedecrease
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Equity Method Investment, Ownership Percentage Before Additional Purchase Transaction + References No definition available. + Details
Name: | biib_EquityMethodInvestmentOwnershipPercentageBeforeAdditionalPurchaseTransaction
Namespace Prefix: | biib_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of net unrealized gain (loss) related to the change in fair value of foreign currency exchange rate derivatives designated as cash flow hedging instruments. Recorded in accumulated other comprehensive income to the extent that the cash flow hedge is determined to be effective. + References No definition available. + Details
Name: | biib_UnrealizedGainLossesOnForeignCurrencyDerivativesNetBeforeTax
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Unrealized Gain on Derivatives + References No definition available. + Details
Name: | biib_UnrealizedGainOnDerivatives
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Unrealized Loss on Derivatives + References No definition available. + Details
Name: | biib_UnrealizedLossOnDerivatives
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 22 -URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI https://asc.fasb.org/extlink&oid=121570589&loc=SL51823488-111719 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624163-113959 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI https://asc.fasb.org/extlink&oid=121570589&loc=SL51823488-111719 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624163-113959 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 22 -URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -Subparagraph (a)(1),(2) -URI https://asc.fasb.org/extlink&oid=121577467&loc=d3e76258-113986 + Details
Name: | us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959 + Details
Name: | us-gaap_DerivativeNotionalAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_DerivativeRemainingMaturity1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
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_DerivativesFairValueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
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 https://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 Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959 + Details
Name: | us-gaap_GainLossOnDerivativeInstrumentsNetPretax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated as hedging instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959 + Details
Name: | us-gaap_GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 15 -URI https://asc.fasb.org/extlink&oid=126968391&loc=d3e689-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI https://asc.fasb.org/extlink&oid=126968391&loc=d3e637-108580 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) in the cumulative translation adjustment from gain (loss), after tax, on foreign currency derivatives, that are designated as, and are effective as, economic hedges of a net investment in a foreign entity. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -URI https://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900 + Details
Name: | us-gaap_TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + 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 https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 + Details
Name: | us-gaap_UnrealizedGainLossOnDerivatives
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherNoncurrentAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_AccruedLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_NetInvestmentHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherNoncurrentLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_SalesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=biib_CashflowsrevenueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_OperatingExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=biib_CashflowsoperatingexpensesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_OtherNonoperatingIncomeExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CurrencyAxis=currency_EUR
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CurrencyAxis=currency_CHF
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CurrencyAxis=currency_JPY
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CurrencyAxis=currency_CAD
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | biib_DerivativeMaturityAxis=biib_ShorttermderivativeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |