Stock-Based Compensation (Details 4) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Number of Shares
Outstanding at the beginning of the period (in shares)	18,066
Granted (in shares)	3,076
Exercised (in shares)	(499)
Forfeited (in shares)	(196)
Outstanding at the end of the period (in shares)	20,447	18,066
Number of stock option exercisable	14,560
Number of shares vested and expected to vest	20,026
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 3.50
Granted (in dollars per share)	$ 6.24
Exercised (in dollars per share)	$ 2.41
Forfeited (in dollars per share)	$ 5.94
Outstanding at the end of the period (in dollars per share)	$ 3.91	$ 3.50
Weighted average exercise price for exercisable option (in dollars per share)	$ 2.85
Weighted average exercise price of shares vested and expected to vest (in dollars per share)	$ 3.85
Weighted Average Remaining Contractual Term
Outstanding at the beginning of the period	6 years 7 months 2 days	6 years 6 months 14 days
Outstanding at the end of the period	6 years 7 months 2 days	6 years 6 months 14 days
Exercisable	5 years 6 months 11 days
Vested and expected to vest	6 years 6 months 11 days
Aggregate Intrinsic Value
Outstanding at the beginning of the period (in dollars)	$ 51,486
Outstanding at the end of the period (in dollars)	60,107	51,486
Options exercisable (in dollars)	57,350
Shares vested and expected to vest (in dollars)	$ 59,982