Stock-Based Compensation - Schedule of Stock-Based Compensation Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding beginning balance (in shares)	3,517
Granted (in shares)	6,698
Exercised (in shares)	(18)
Canceled/Forfeited (in shares)	(296)
Outstanding ending balance (in shares)	9,901
Exercisable at December 31, 2012 (in shares)	3,081	[1]
Vested at December 31, 2012 (in shares)	9,423
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding weighted average exercise price, beginning balance (in usd per share)	$ 4.01
Weighted average fair value of options outstanding (in usd per share)	$ 1.94
Exercised weighted average exercise price (in usd per share)	$ 1.86
Canceled/Forfeited weighted average exercise price (in usd per share)	$ 3.24
Outstanding weighted average exercise price, ending balance (in usd per share)	$ 2.64
Exercisable weighted average exercise price (in usd per share)	$ 3.13	[1]
Vested weighted average exercise price (in usd per share)	$ 2.66
Outstanding, weighted average remaining term	8 years 9 months 7 days
Exercisable, weighted average remaining term	8 years	[1]
Vested, weighted average remaining term	8 years 9 months
Outstanding, intrinsic value	$ 39
Exercisable, intrinsic value	39	[1]
Vested, intrinsic value	$ 39

[1] Includes awards with early exercise provisions that permit optionee to exercise unvested options.