Stock-Based Compensation - Stock Option Plan Activity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Outstanding Shares
Beginning balance (in shares)	7,039,093
Granted (in shares)	1,399,400
Exercised (in shares)	(598,670)
Canceled (in shares)	(529,268)
Ending balance (in shares)	7,310,555	7,039,093
Vested and expected to vest (in shares)	6,802,381
Exercisable (in shares)	4,870,019
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 7.17
Weighted average exercise price, granted (in dollars per share)	$ 23.65
Weighted average exercise price, exercised (in dollars per share)	$ 5.10
Weighted average exercise price, canceled (in dollars per share)	$ 16.81
Ending balance (in dollars per share)	$ 9.80	$ 7.17
Vested and expected to vest (in dollars per share)	$ 9.18
Exercisable (in dollars per share)	$ 4.70
Weighted Average Remaining Contractual Life
Weighted average remaining contractual life	6 years 4 months 27 days	6 years 6 months
Vested and expected to vest	6 years 3 months
Exercisable	5 years 3 months 18 days
Aggregate Intrinsic Value
Aggregate intrinsic value	$ 116,943	$ 112,312
Vested and expected to vest	112,981
Exercisable	$ 102,123