Stock-Based Compensation (Details 2) (USD $)	3 Months Ended		6 Months Ended					12 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Stock options	Jun. 30, 2012 RSUs	Jun. 30, 2012 RSAs	Dec. 31, 2011 RSAs Employee Performance-Contingent Senior management	Jun. 30, 2012 Research and development	Jun. 30, 2011 Research and development	Jun. 30, 2012 Research and development	Jun. 30, 2011 Research and development	Dec. 31, 2011 Research and development RSAs Employee Performance-Contingent Senior management	Jun. 30, 2012 General and administrative	Jun. 30, 2011 General and administrative	Jun. 30, 2012 General and administrative	Jun. 30, 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	$ 5,979,000	$ 6,275,000	$ 12,214,000	$ 11,816,000					$ 3,541,000	$ 3,379,000	$ 7,070,000	$ 6,511,000		$ 2,438,000	$ 2,896,000	$ 5,144,000	$ 5,305,000
Information related to share-based compensation
Timeframe for performance targets								6 years
Total unrecognized compensation cost related to unvested stock-based compensation					6,800,000	19,800,000	27,100,000
Maximum potential expenses associated with 2011 performance-contingent restricted stock grant								$ 31,900,000					$ 6,300,000					$ 25,600,000