Collaboration Agreements (Period End Balances) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 10,715.8	$ 4,067.6
Acceleron
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	0.0	0.0
Equity Investment Balance	$ 114.8	$ 179.7
Percentage of Outstanding Equity	14.00%	14.00%
Acetylon
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 5.8	$ 20.4
Equity Investment Balance	$ 25.0	$ 25.0
Percentage of Outstanding Equity	11.00%	10.00%
bluebird
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 1.0	$ 0.0
Equity Investment Balance	$ 370.1	$ 587.4
Percentage of Outstanding Equity	13.00%	14.00%
Epizyme
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 22.3	$ 0.1
Epizyme
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	0.0	0.0
Equity Investment Balance	$ 47.3	$ 69.3
Percentage of Outstanding Equity	8.00%	11.00%
FORMA
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 0.1	$ 0.1
Juno Therapeutics, Inc
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	0.0
Equity Investment Balance	$ 371.8
Percentage of Outstanding Equity	9.00%
Sutro
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 3.0
Equity Investment Balance	$ 10.0
Percentage of Outstanding Equity	8.00%
MorphoSys
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 0.0	0.0
Equity Investment Balance	$ 53.1	$ 73.9
Percentage of Outstanding Equity	3.00%	3.00%
NantBioScience
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 0.0	$ 0.0
Equity Investment Balance	$ 90.0	$ 90.0
Percentage of Outstanding Equity	13.00%	14.00%
Nurix, Inc
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 0.2
Equity Investment Balance	$ 17.0
Percentage of Outstanding Equity	13.00%
Sutro Biopharma, Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 24.4	$ 12.8
Equity Investment Balance	$ 17.6	$ 17.6
Percentage of Outstanding Equity	15.00%	15.00%
Other Collaboration Arrangements
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 22.1	$ 34.4
Equity Investment Balance	$ 130.1	$ 90.8

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.

No definition available.

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- 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

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

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- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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-Publisher FASB

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