September 2009 Financial Transactions (Details) (USD $)	1 Months Ended		3 Months Ended	12 Months Ended
	Feb. 28, 2011	Sep. 30, 2009 agreements	Sep. 30, 2009	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Oct. 31, 2011
2012 Notes
Face amount of 2012 Notes			$ 155,000,000
Proceeds from issuance of 2012 Notes			122,200,000
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
Value of potential contingent launch milestone payments sold pursuant to the Janssen collaboration		95,000,000
Proceeds from sale of potential contingent launch milestone payments pursuant to the Janssen collaboration		32,800,000
Expenses and Losses (Gains):
Interest expense related to 2012 Notes				0	21,687,000	15,068,000
Change in fair value of embedded derivative related to 2012 Notes				0	(400,000)	1,637,000
Change in fair value of free-standing derivatives related to the sale of milestone payments				0	17,201,000	39,592,000
Total September 2009 financial transaction expenses				$ 0	$ 38,488,000	$ 56,297,000