Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock options, Outstanding, balance	11,408,000
Stock options, Granted	2,863,000
Stock options, Exercised	(854,000)
Stock options, Cancelled/Forfeited	(783,000)
Stock options, Outstanding, Balance	12,634,000	11,408,000
Stock options, Options vested and exercisable	5,414,000
Stock options, Options vested and expected to vest	10,480,000
Weighted-average exercise price, Outstanding, Balance	$ 4.42
Weighted-average exercise price, Granted	9.17
Weighted-average exercise price, Exercised	2.79
Weighted-average exercise price, Cancelled/Forfeited	5.00
Weighted-average exercise price, Outstanding, Balance	5.57	$ 4.42
Weighted-average exercise price, Options vested and exercisable	3.63
Weighted-average exercise price, Options vested and expected to vest	$ 5.31
Weighted-average remaining contractual life, options outstanding	7 years 1 month 6 days	8 years 2 months 12 days
Weighted-average remaining contractual life, options vested and exercisable	6 years 2 months 12 days
Weighted-average remaining contractual life, options vested and expected to vest	8 years 1 month 6 days