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Biogen share of co-promotion profits or losses

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Developmental Milestone Payment

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License Fee

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Percentage of royalties as per collaboration.

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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

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Royalty expense incurred and are directly related to goods produced and sold and services rendered during the reporting period.

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Amount of increase (decrease) in carrying value of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount, after sales adjustments, returns, allowances, and discounts, of revenue classified as other.

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The costs incurred 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 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, excluding in-process research and development acquired in a business combination consummated during the period. Excludes software research and development, which has a separate concept.

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Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

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Amount of unrecognized tax benefits.

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Collaborative and Other Relationships Collaborative and Other Relationships - Collaborations (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development	$ 446.4		$ 529.0	$ 1,666.0	$ 1,439.4
ZINBRYTA related assets	23,073.2			23,073.2		$ 22,876.8
Other	48.8		98.6	180.4	265.5
Collaboration profit (loss) sharing	35.2		4.7	82.5	(0.9)
Product, net	2,622.5		2,539.6	7,642.3	7,315.0
ZINBRYTA
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
ZINBRYTA related assets	200.0			200.0
Unrecorded tax benefit	100.0			100.0
Bristol-Myers Squibb
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development				300.0
Additional milestone payments	410.0			410.0
iPerian
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional milestone payments	490.0			490.0
Developmental Milestone Payment	60.0			$ 60.0
AbbVie
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Biogen share of co-promotion profits or losses				50.00%
AbbVie \| U.S.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Other	2.8			$ 12.6	13.5
AbbVie \| Rest of world
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration profit (loss) sharing	0.7			2.0	2.7
Ionis Pharmaceuticals [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License Fee			75.0
Ionis Pharmaceuticals [Member] \| SPINRAZA
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Direct Operating Cost, Royalty Expense	34.0			64.9
Ionis Pharmaceuticals [Member] \| SPINRAZA \| U.S.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Product, net	197.6			438.8
Ionis Pharmaceuticals [Member] \| SPINRAZA \| Rest of world
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Product, net			$ 73.3		$ 82.4
Acquired and in-licensed rights and patents \| SPINRAZA
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase in acquired and in-licensed rights and patents	$ 40.0	$ 50.0		$ 150.0
Minimum \| Ionis Pharmaceuticals [Member] \| SPINRAZA
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty payments per the collaboration				11.00%
Maximum \| Ionis Pharmaceuticals [Member] \| SPINRAZA
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty payments per the collaboration				15.00%