Stock-Based Compensation (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock-based compensation
Stock options issued (in shares)	3,251,000
2008 Plan
Stock-based compensation
Common stock available for issuance (in shares)		830,000
2011 Plan
Stock-based compensation
Common stock available for issuance (in shares)	1,300,000
Additional common stock available for issuance (in shares)	3,500,000
2011 Plan | Director
Stock-based compensation
Vesting period	1 year
2008 Plan and 2011 Plan
Stock-based compensation
Stock options issued (in shares)	3,300,000	2,300,000	2,900,000
2008 Plan and 2011 Plan | Employee
Stock-based compensation
Vesting period	3 years
2008 Plan and 2011 Plan | Non-employee | Maximum
Stock-based compensation
Stock options issued (in shares)	100,000	100,000	100,000