Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock options, Outstanding, balance	12,795,000	11,408,000
Stock options, Granted	3,674,000	3,806,000
Stock options, Exercised	(1,852,000)	(1,210,000)
Stock options, Cancelled/Forfeited	(1,720,000)	(1,209,000)
Stock options, Outstanding, Balance	12,897,000	12,795,000	11,408,000
Stock options, Options vested and exercisable	6,763,000
Stock options, Options vested and expected to vest	10,886,000
Weighted-average exercise price, Outstanding, Balance	$ 5.89	$ 4.42
Weighted-average exercise price, Granted	5.73	9.50
Weighted-average exercise price, Exercised	2.94	2.96
Weighted-average exercise price, Cancelled/Forfeited	8.37	6.27
Weighted-average exercise price, Outstanding, Balance	5.94	$ 5.89	$ 4.42
Weighted-average exercise price, Options vested and exercisable	5.19
Weighted-average exercise price, Options vested and expected to vest	$ 5.80
Weighted-average remaining contractual life, Options outstanding	7 years 5 months 27 days	7 years 9 months 26 days	8 years 2 months 12 days
Weighted-average remaining contractual life, Options vested and exercisable	6 years 4 months 24 days
Weighted-average remaining contractual life, Options vested and expected to vest	7 years 3 months
Aggregate intrinsic value, Options outstanding	$ 9,625	$ 75,797
Aggregate intrinsic value, Options vested and exercisable	8,943
Aggregate intrinsic value, Options vested and expected to vest	$ 9,435