September 2009 Financial Transactions (Details) (USD $)	1 Months Ended		3 Months Ended		6 Months Ended
	Feb. 28, 2011	Sep. 30, 2009	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 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			105,000,000		105,000,000
Portion of 2012 Notes that will be redeemed upon achievement of certain approval milestone pursuant to the Janssen collaboration			50,000,000		50,000,000
Redemption of 2012 Notes	50,000,000
Portion of 2012 Notes that will be redeemed upon achievement of certain launch milestones pursuant to the Janssen collaboration			55,000,000		55,000,000
Percent of outstanding 2012 Notes face amount due upon change of control call of notes (as a percent)			100.00%		100.00%
Percent of outstanding 2012 Notes face amount due upon early redemption (as a percent)			100.00%		100.00%
Minimum amount of outstanding 2012 Notes required to declare 2012 Notes due in event of default (as a percent)			25.00%		25.00%
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
Value of potential future launch milestone payments sold pursuant to the Janssen collaboration		95,000,000
Proceeds from sale of potential future launch milestone payments pursuant to the Janssen collaboration		32,800,000
Expenses and Losses (Gains):
Interest expense related to 2012 Notes			2,863,000	3,702,000	10,797,000	7,285,000
Change in fair value of embedded derivative related to 2012 Notes			(18,000)	3,528,000	(1,514,000)	3,848,000
Change in fair value of free-standing derivatives related to sale of potential future launch milestone payments			2,238,000	23,706,000	9,332,000	24,875,000
Total September 2009 financial transaction expenses			5,083,000	30,936,000	18,615,000	36,008,000
Liabilities:
2012 Notes, excluding fair value of embedded derivative			89,691,000		89,691,000		124,902,000
Embedded derivative related to 2012 Notes			4,973,000		4,973,000		12,089,000
Liability related to the sale of potential future milestone payments			87,131,000		87,131,000		77,799,000
Total liabilities related to September 2009 financial transactions			$ 181,795,000		$ 181,795,000		$ 214,790,000