XML 116 R78.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Collaborative and Other Relationships Collaborative and Other Relationships - Equity Method Investments (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended
--- | --- | ---
Feb. 29, 2012 | Mar. 31, 2018 | Mar. 31, 2017
Schedule of Equity Method Investments [Line Items] |  |  |
Collaboration profit (loss) sharing |  | $ 42.5 | $ 20.8
Revenue related to technical development and technology transfer services |  | $ 164.4 | 90.0
Samsung Bioepis |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Percentage of stake in entity |  | 5.40% |
Percentage of stake in entity maximum | 49.90% |  |
Biogen share of co-promotion profits or losses |  | 50.00% |
Collaboration profit (loss) sharing |  | $ 43.8 | 20.8
Revenue related to technical development and technology transfer services |  | $ 17.9 | $ 2.2

X
- Definition Biogen share of co-promotion profits or losses + References No definition available. + Details
Name: | biib_Biogenshareofcopromotionprofitsorlosses
Namespace Prefix: | biib_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Collaboration profit (loss) sharing + References No definition available. + Details
Name: | biib_Collaborationprofitlosssharing
Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Equity method investment ownership percentage maximum. + References No definition available. + Details
Name: | biib_EquityMethodInvestmentOwnershipPercentageMaximum
Namespace Prefix: | biib_
Data Type: | num: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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount, after sales adjustments, returns, allowances, and discounts, of revenue classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1(a),(d)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_OtherSalesRevenueNet
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_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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