XML 150 R86.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Indebtedness (Details Textual) SFr in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2008 USD ($) | Dec. 31, 2017 USD ($) | Sep. 30, 2015 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2017 CHF (SFr) | Dec. 31, 2016 USD ($) | Dec. 31, 2016 CHF (SFr) | Mar. 04, 2008 USD ($) | Dec. 31, 2006 CHF (SFr)
Debt Instrument |  |  |  |  |  |  |  |  |  |
Net charge upon extinguishment of debt |  | $ 5,200,000 |  |  |  |  |  |  |  |
Payment for debt extinguishment |  | 7,700,000 |  |  |  |  |  |  |  |
Costs associated with the Senior Notes offerings |  |  |  |  | $ 47,500,000 |  |  |  |  |
Redemptions percentage of 2015 notes |  |  |  | 100.00% |  |  |  |  |  |
Redemption percentage for change in control provision on the 2015 Senior Notes |  |  |  | 101.00% |  |  |  |  |  |
Notes payable and other financing arrangements |  | 6,003,200,000 |  | $ 6,003,200,000 |  |  |  |  |  |
Senior unsecured revolving credit facility maximum borrowing capacity |  |  |  |  | $ 1,000,000,000 |  |  |  |  |
Term of credit facility |  |  |  |  | 5 years |  |  |  |  |
Amount outstanding under the credit facility |  | $ 0 |  | $ 0 |  |  |  |  |  |
6.875% Senior Notes due 2018 |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Interest rate on senior notes |  | 6.875% |  | 6.875% |  | 6.875% |  |  | 6.875% |
Redemption percentage par value of senior notes |  |  |  |  |  |  |  |  | 99.184% |
Increased carrying amount of interest rate swap | $ 62,800,000 |  |  |  |  |  |  |  |  |
Senior Notes aggregate principal amount |  |  |  |  |  |  |  |  | $ 550,000,000 |
Notes payable and other financing arrangements |  | $ 0 |  | $ 0 |  |  | $ 558,500,000 |  |  |
2.90% Senior Notes due 2020 |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Interest rate on senior notes |  | 2.90% |  | 2.90% | 2.90% | 2.90% |  |  |  |
Redemption percentage par value of senior notes |  |  |  |  | 99.792% |  |  |  |  |
Senior Notes aggregate principal amount |  |  |  |  | $ 1,500,000,000 |  |  |  |  |
Notes payable and other financing arrangements |  | $ 1,482,400,000 |  | $ 1,482,400,000 |  |  | 1,485,300,000 |  |  |
3.625% Senior Notes due 2022 |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Interest rate on senior notes |  | 3.625% |  | 3.625% | 3.625% | 3.625% |  |  |  |
Redemption percentage par value of senior notes |  |  |  |  | 99.92% |  |  |  |  |
Senior Notes aggregate principal amount |  |  |  |  | $ 1,000,000,000 |  |  |  |  |
Notes payable and other financing arrangements |  | $ 994,300,000 |  | $ 994,300,000 |  |  | 993,200,000 |  |  |
4.05% Senior Notes due 2025 |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Interest rate on senior notes |  | 4.05% |  | 4.05% | 4.05% | 4.05% |  |  |  |
Redemption percentage par value of senior notes |  |  |  |  | 99.764% |  |  |  |  |
Senior Notes aggregate principal amount |  |  |  |  | $ 1,750,000,000 |  |  |  |  |
Notes payable and other financing arrangements |  | $ 1,736,300,000 |  | $ 1,736,300,000 |  |  | 1,734,800,000 |  |  |
5.20% Senior Notes due 2045 |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Interest rate on senior notes |  | 5.20% |  | 5.20% | 5.20% | 5.20% |  |  |  |
Redemption percentage par value of senior notes |  |  |  |  | 99.294% |  |  |  |  |
Senior Notes aggregate principal amount |  |  |  |  | $ 1,750,000,000 |  |  |  |  |
Notes payable and other financing arrangements |  | $ 1,722,000,000 |  | $ 1,722,000,000 |  |  | 1,721,500,000 |  |  |
Note payable to Fumedica |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Notes payable and other financing arrangements |  | 0 |  | 0 |  |  | 3,000,000 |  |  | SFr 61.4
Par value of notes payable |  | 3,200,000 |  | 3,200,000 |  | SFr 3.1 | $ 6,000,000 | SFr 6.2 |  |
Interest rate swap |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Net charge upon extinguishment of debt |  | 2,900,000 |  |  |  |  |  |  |  |
Interest rate swap | 2.90% Senior Notes due 2020 |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Fair value of the interest rate swaps |  | 10,100,000 |  | $ 10,100,000 |  |  |  |  |  |
Eisai |  |  |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |  |  |
Facility purchase |  | $ 17,200,000 | $ 104,800,000 |  |  |  |  |  |  |

X
- Definition Debt Instrument, Make Whole Provision Redemption Price, Percentage + References No definition available. + Details
Name: | biib_DebtInstrumentMakeWholeProvisionRedemptionPricePercentage
Namespace Prefix: | biib_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Increased carrying amount of senior notes. + References No definition available. + Details
Name: | biib_IncreasedCarryingAmountOfSeniorNotes
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Par value of notes payable. + References No definition available. + Details
Name: | biib_ParValueOfNotesPayable
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage Par Value Of Senior Notes + References No definition available. + Details
Name: | biib_PercentageParValueOfSeniorNotes
Namespace Prefix: | biib_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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
- 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_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage price of original principal amount of debt at which debt can be redeemed by the issuer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph e -URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823 + Details
Name: | us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
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=84234895&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=82849420&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=82924980&loc=SL51823488-111719 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The difference between the reacquisition price and the net carrying amount of the extinguished debt recognized currently as a component of income in the period of extinguishment, net of tax. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629 + Details
Name: | us-gaap_ExtinguishmentOfDebtGainLossNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Period remaining on line of credit facility before it terminates, 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_LineOfCreditFacilityExpirationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of the amount outstanding under the credit facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13476-108611 + Details
Name: | us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + 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 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying value as of the balance sheet date of notes payable (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. + 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) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermNotesPayable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585 + Details
Name: | us-gaap_PaymentsOfDebtExtinguishmentCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash outflow for loan and debt issuance costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585 + Details
Name: | us-gaap_PaymentsOfFinancingCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of acquisition of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentAdditions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DebtInstrumentAxis=biib_SeniorNotesSixPointEightSevenFivePercentDueTwentyEighteenMember
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_DebtInstrumentAxis=biib_SeniorNotesThreePointSixTwoFivePercentDueTwentyTwentyTwoMember
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=us-gaap_NotesPayableOtherPayablesMember
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_BusinessAcquisitionAxis=biib_EisaiMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |