XML 107 R64.htm IDEA: XBRL DOCUMENT
v3.3.0.814

Derivative Instruments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014 | Dec. 31, 2014
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Lower range of durations of foreign currency forward contracts |  |  | 1 month |  | 1 month
Higher range of durations of foreign currency forward contracts |  |  | 15 months |  | 15 months
Gain/Loss on fair value of foreign currency forward contracts | $ 23.3 |  | $ 23.3 |  | $ 72.1
Expected settlement time for contracts, in months |  |  | 15 months |  |
Gain for treasury rate lock settlement |  |  | $ 19.7 | $ (11.0) |
Net gains (losses) of other income (expense) related to foreign currency forward contracts | 8.1 | $ 7.7 | 4.2 | 11.5 |
Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount |  |  |  |  | 1,302.3
Not designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | 787.2 |  | 787.2 |  | 365.2
Other current assets | Designated as hedging instrument |  |  |  |  |
Summary of Derivatives designated as Hedging Instruments |  |  |  |  |
Derivative asset, fair value, net | 54.1 |  | 54.1 |  | 69.5
Investments and other assets | Designated as hedging instrument |  |  |  |  |
Summary of Derivatives designated as Hedging Instruments |  |  |  |  |
Derivative asset, fair value, net | 5.6 |  | 5.6 |  | 1.9
Accrued expenses and other | Designated as hedging instrument |  |  |  |  |
Summary of Derivatives designated as Hedging Instruments |  |  |  |  |
Derivative liability, fair value, net | 17.6 |  | 17.6 |  |
Other long-term liabilities | Designated as hedging instrument |  |  |  |  |
Summary of Derivatives designated as Hedging Instruments |  |  |  |  |
Derivative liability, fair value, net | 8.5 |  | 8.5 |  |
Foreign exchange contract | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | 1,190.2 |  | 1,190.2 |  |
Foreign exchange contract | Other current assets | Not designated as hedging instrument |  |  |  |  |
Summary of Derivatives designated as Hedging Instruments |  |  |  |  |
Derivative asset, fair value, net | 1.7 |  | 1.7 |  | 1.3
Foreign exchange contract | Accrued expenses and other | Not designated as hedging instrument |  |  |  |  |
Summary of Derivatives designated as Hedging Instruments |  |  |  |  |
Derivative liability, fair value, net | 5.2 |  | 5.2 |  | 5.4
Interest rate swap | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | 675.0 |  | 675.0 |  |
Interest rate swap | Investments and other assets | Designated as hedging instrument |  |  |  |  |
Summary of Derivatives designated as Hedging Instruments |  |  |  |  |
Derivative asset, fair value, net | 5.6 |  | 5.6 |  |
Revenue | Foreign exchange contract |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Net gains (losses) in product revenue for the settlement of certain effective cash flow hedge instruments | 43.9 | 2.9 | 119.3 | (7.1) |
Other income (expense) | Foreign exchange contract |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Net gains (losses) in earnings of Foreign currency forward contracts due to hedge ineffectiveness | 2.0 | $ (0.5) | 5.4 | (1.6) |
Euro | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount |  |  |  |  | 1,174.6
Euro | Foreign exchange contract | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | 1,146.1 |  | 1,146.1 |  |
Canadian Dollar | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount |  |  |  |  | 56.7
Canadian Dollar | Foreign exchange contract | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | 17.4 |  | 17.4 |  |
British Pound Sterling | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount |  |  |  |  | 34.5
British Pound Sterling | Foreign exchange contract | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | 12.0 |  | 12.0 |  |
Japanese Yen | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount |  |  |  |  | 16.6
Japanese Yen | Foreign exchange contract | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | 9.3 |  | 9.3 |  |
Australian Dollar | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount |  |  |  |  | $ 19.9
Australian Dollar | Foreign exchange contract | Designated as hedging instrument |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Aggregate notional amount | $ 5.4 |  | $ 5.4 |  |
4.050% Senior Notes due 2025 |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Senior Notes interest rate | 4.05% |  | 4.05% |  |
5.200% Senior Notes due 2045 |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Senior Notes interest rate | 5.20% |  | 5.20% |  |
2.900% Senior Notes due 2020 |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Senior Notes interest rate | 2.90% |  | 2.90% |  |
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Gain for treasury rate lock settlement |  |  | $ 78.6 | $ 57.5 |
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges | Interest rate locks |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Gain for treasury rate lock settlement |  |  | $ 8.5 |  |

X
- Definition Derivative Instruments. + References No definition available. + Details
Name: | biib_DerivativeInstrumentsTextualAbstract
Namespace Prefix: | biib_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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 Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DerivativeAssetFairValueNetAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=51814546&loc=SL51823488-111719 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=51814546&loc=SL51823488-111719 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition High end period remaining until maturity for the derivative contract, 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_DerivativeHigherRemainingMaturityRange1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4D -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624177-113959 + Details
Name: | us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -Subparagraph (a)(1),(2) -URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986 + Details
Name: | us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Low end period remaining until maturity of derivative contract, 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_DerivativeLowerRemainingMaturityRange1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5618551-113959 + Details
Name: | us-gaap_GainLossOnForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstruments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Maximum amount of time remaining before foreign currency exchange rate derivatives mature or expire, 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_MaximumRemainingMaturityOfForeignCurrencyDerivatives1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount after tax, before reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=51821188&loc=d3e1436-108581 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
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_BalanceSheetLocationAxis=us-gaap_OtherInvestmentsMember
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_BalanceSheetLocationAxis=us-gaap_OtherNoncurrentLiabilitiesMember
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_InterestRateSwapMember
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_IncomeStatementLocationAxis=us-gaap_OtherNonoperatingIncomeExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | us-gaap_CurrencyAxis=currency_GBP
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_CurrencyAxis=currency_AUD
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=biib_SeniorNotesFourPointZeroFivePercentDueTwentyTwentyFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=biib_SeniorNotesFivePointTwoPercentDueTwentyFortyFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=biib_SeniorNotesTwoPointNinePercentDueTwentyTwentyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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