Stock-Based Compensation (Details 2) (USD $)	3 Months Ended					12 Months Ended		3 Months Ended		12 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Stock options	Mar. 31, 2012 RSUs	Mar. 31, 2012 RSAs	Dec. 31, 2011 RSAs Employee Performance-Contingent Senior management Y	Mar. 31, 2012 RSAs Employee Performance-Contingent Senior management	Mar. 31, 2012 Research and development	Mar. 31, 2011 Research and development	Dec. 31, 2011 Research and development RSAs Employee Performance-Contingent Senior management	Mar. 31, 2012 General and administrative	Mar. 31, 2011 General and administrative	Dec. 31, 2011 General and administrative RSAs Employee Performance-Contingent Senior management
Allocation of stock-based compensation expense
Stock-based compensation expense	$ 6,235,000	$ 5,541,000						$ 3,529,000	$ 3,132,000		$ 2,706,000	$ 2,409,000
Information related to share-based compensation
Shares of common stock approved and authorized for issuance						1,290,000	44,500
Timeframe for performance targets (in years)						6
Total unrecognized compensation cost related to unvested stock-based compensation			7,000,000	21,900,000	29,100,000
Maximum potential expenses associated with 2011 performance-contingent restricted stock grant						$ 31,900,000				$ 6,300,000			$ 25,600,000