September 2009 Financial Transactions (Details) (USD $)	1 Months Ended			3 Months Ended		9 Months Ended
	Oct. 31, 2011	Feb. 28, 2011	Sep. 30, 2009 agreements	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
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
Outstanding aggregate amount of 2012 Notes payable oligated to be paid when the fourth quarter 2011 milestone payment is received				105,000,000		105,000,000
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 Future Milestone Payments
Number of purchase agreements entered into related to sale of potential future launch milestone payments pursuant to the Janssen collaboration			2
Proceeds from sale of potential future launch milestone payments pursuant to the Janssen collaboration			32,800,000
Value of potential future launch milestone payments sold pursuant to the Janssen collaboration	95,000,000
Expenses and Losses (Gains):
Interest expense related to 2012 Notes				2,960,000	3,827,000	13,757,000	11,112,000
Change in fair value of embedded derivative related to 2012 Notes				1,084,000	(3,130,000)	(430,000)	718,000
Change in fair value of free-standing derivatives related to sale of future launch milestone payments				7,031,000	9,041,000	16,363,000	33,916,000
Total September 2009 financial transaction expenses				11,075,000	9,738,000	29,690,000	45,746,000
Liabilities:
2012 Notes, excluding fair value of embedded derivative				92,359,000		92,359,000		124,902,000
Embedded derivative related to 2012 Notes				6,057,000		6,057,000		12,089,000
Liability related to the sale of future milestone payments				94,162,000		94,162,000		77,799,000
Total liabilities related to September 2009 financial transactions				$ 192,578,000		$ 192,578,000		$ 214,790,000