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v3.19.3

Leases (Details Textual) - USD ($) $ in Millions | Sep. 30, 2019 | Aug. 01, 2019
--- | --- | ---
Minimum |  |
Operating Leased Assets [Line Items] |  |
Lessee, Operating Lease, Term of Contract | 1 year |
Lessee, Operating Lease, Renewal Term | 1 year |
Maximum |  |
Operating Leased Assets [Line Items] |  |
Lessee, Operating Lease, Term of Contract | 9 years |
Lessee, Operating Lease, Renewal Term | 6 years |
Denmark Manufacturing Operations |  |
Operating Leased Assets [Line Items] |  |
Operating lease assets |  | $ 2.2
Operating lease liabilities |  | $ 2.2

X
- Definition Disposal Group, Operating Lease Assets + References No definition available. + Details
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Namespace Prefix: | biib_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Disposal Group, Operating lease liabilities + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | instant

X
- Definition Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
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Balance Type: | na
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- 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
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Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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- Details
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Namespace Prefix: |
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