September 2009 Financial Transactions (Details) (USD $)	1 Months Ended			12 Months Ended
	Oct. 31, 2011	Feb. 28, 2011	Sep. 30, 2009 agreements	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
2012 Notes
Face amount of 2012 Notes			$ 155,000,000
Proceeds from issuance of 2012 Notes			122,200,000
Security interest in future milestone payments pursuant to the Janssen collaboration			155,000,000
Proceeds from milestone payment related to the acceptance of Janssen's MAA		50,000,000
Portion of 2012 Notes redeemed upon achievement of certain approval milestone pursuant to the Janssen collaboration				50,000,000
Earned remaining milestone payment to be received in the fourth quarter of 2011	105,000,000
Sale of Contingent Milestone Payments
Number of purchase agreements entered into related to sale of contingent launch milestone payments pursuant to the Janssen collaboration			2
Proceeds from sale of potential contingent launch milestone payments pursuant to the Janssen collaboration			32,800,000
Value of potential contingent launch milestone payments sold pursuant to the Janssen collaboration	95,000,000
Expenses and Losses (Gains):
Interest expense related to 2012 Notes				21,687,000	15,068,000	3,465,000
Change in fair value of embedded derivative related to 2012 Notes				(400,000)	1,637,000	(200,000)
Change in fair value of free-standing derivatives related to the sale of milestone payments				17,201,000	39,592,000	2,047,000
Total September 2009 financial transaction expenses				38,488,000	56,297,000	5,312,000
Liabilities:
2012 Notes, excluding fair value of embedded derivative					124,902,000
Embedded derivative related to 2012 Notes					12,089,000
Derivatives related to the sale of milestone payments					77,799,000
Total liabilities related to September 2009 financial transactions					$ 214,790,000