Collaboration Agreements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Collaboration Agreements Transactions
Research and development	$ 452.4	$ 362.0
Bluebird
Collaboration Agreements Transactions
Co-development and profit share in exchange for a reduction of milestones	0.50
Notice period required to be given before termination of agreement	90 days
Bluebird \| Maximum
Collaboration Agreements Transactions
Potential milestone payments per product	225.0
Other Collaboration Arrangements
Collaboration Agreements Transactions
Investments in equity or other assets	5.3
Other Collaboration Arrangements \| Maximum
Collaboration Agreements Transactions
Potential milestone payments	45.0
All Collaboration Agreements Partners
Collaboration Agreements Transactions
Research and development	$ 95.7

Represents the ratio of co-development and profit share in exchange for a reduction of milestones.

No definition available.

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- Definition

Represents the notice period required to be served before the termination of the agreement.

+ References

No definition available.

+ Details

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- Definition

Represents the investment in common stock under equity method and in other assets.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the potential payment that the entity is eligible to pay for certain milestone(s), which may include development, regulatory approval or sales-based milestones under the agreement.

+ References

No definition available.

+ Details

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- Definition

Represents the potential payment per product that the entity is eligible to pay for certain milestone(s), which may include development, regulatory approval or sales-based milestones under the agreement.

+ References

No definition available.

+ Details

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- Details

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- Definition

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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 86

-Paragraph 3

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 2

-Paragraph 8, 12, 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 86

-Paragraph 11

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: 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

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Research and Development

-URI http://asc.fasb.org/extlink&oid=6523717

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration