Investment in biotechnology companies that are determined to be unconsolidated variable interest entities.

No definition available.

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- Details

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- Definition

Milestone Payments Made During Period.

+ References

No definition available.

+ Details

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- Definition

Net income loss attributable to noncontrolling interest percentage.

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No definition available.

+ Details

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- Definition

Percentage of operations from joint-venture investments reflected in the consolidated financial statements.

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No definition available.

+ Details

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- Definition

Amount of cash paid to acquire stock of the entity.

+ References

No definition available.

+ Details

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- Definition

Purchase of common shares in variable interest entities.

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No definition available.

+ Details

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- Definition

Expected total payments including upfront and milestone payments as well as the greater of an annual maintenance fee or usage-based royalty payments under the terms of collaboration agreement.

+ References

No definition available.

+ Details

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- Definition

Research and development cost in support of the collaboration agreement.

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No definition available.

+ Details

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- Definition

Total upfront and reimbursement payment made to collaborative partner.

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No definition available.

+ Details

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Namespace Prefix:	biib_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 730

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

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Investments in Variable Interest Entities (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investment in Variable Interest Entities (Textual)
Percentage of operations of joint venture investments on financial statements			100.00%
Percentage of net income (loss) attributable to noncontrolling interests			50.00%
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities	$ 5.5	$ 9.4
Knopp
Investment in Variable Interest Entities (Textual)
Total upfront and reimbursement payment made to collaborative partner				26.4
Purchase consideration for variable interest entities				60.0
Research and development expense		12.3
Percentage of funding for R&D cost required in support of the collaboration agreement	100.00%
Milestone payments made during period	0	0	10.0
Neurimmune
Investment in Variable Interest Entities (Textual)
Percentage of funding for R&D cost required in support of the collaboration agreement	100.00%
Remaining potential development milestone payments and royalties on commercial sales under the terms of collaboration agreement	345.0
Milestone payments made during period	$ 0	$ 0	$ 15.0
Common Class B \| Knopp
Investment in Variable Interest Entities (Textual)
Purchase of common shares in variable interest entities				30.00%