Subsequent Events (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 License, Development and Commercialization Agreement With Astellas	Feb. 29, 2012 Shares issued	Dec. 31, 2011 Contract termination License, Development and Commercialization Agreement With Astellas
Information related to subsequent events
Percentage of royalties payable to Astellas			2.00%
Remaining non-cash deferred upfront license fees and milestone payments					$ 125,000,000
Future inventory cost			11,000,000
Agreement to issue stock in private placement, number of shares				88,468
Agreement to issue stock in private placement, price per share (in dollars per share)				$ 18.12
Issuance of common stock for cash in private placement to a related party	$ 13,618,000	$ 129,190,000		$ 1,600,000