Net Product Sales (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Revenue Disclosure [Line Items]
Net product sales	$ 318,740	$ 127,931
Activity of Sales Related Deductions [Roll Forward]
Balance as of December 31, 2011	18,826
Provision related to current period sales	19,661
Credits/payments	(16,583)
Balance as of December 31, 2012	21,904
Rebates and Chargebacks
Activity of Sales Related Deductions [Roll Forward]
Balance as of December 31, 2011	2,983
Provision related to current period sales	5,537
Credits/payments	(4,844)
Balance as of December 31, 2012	3,676
Distribution Related Fees
Activity of Sales Related Deductions [Roll Forward]
Balance as of December 31, 2011	15,298
Provision related to current period sales	13,916
Credits/payments	(11,521)
Balance as of December 31, 2012	17,693
Other Sales Related Deductions
Activity of Sales Related Deductions [Roll Forward]
Balance as of December 31, 2011	545
Provision related to current period sales	208
Credits/payments	(218)
Balance as of December 31, 2012	535
EYLEA
Revenue Disclosure [Line Items]
Net product sales	313,900	123,500
ARCALYST
Revenue Disclosure [Line Items]
Net product sales	$ 4,800	$ 4,400
GrossSalesRevenue \| Customer concentration risk
Risks and Uncertainties [Abstract]
Concentration risk, percentage	77.00%	81.00%

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Percentage of revenue generated from a single external customer that accounts for 10 percent or more of an entity's revenues.

+ References

No definition available.

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(a))

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e24092-122690

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Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

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