Stock-based Compensation - Summary of Stock Option Activity and Related Information (Detail) - Stock Option [Member] - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option activity, shares outstanding, at beginning of period	3,012,923
Stock option activity, shares granted	1,466,500
Stock option activity, shares exercised	(37,225)
Stock option activity, shares canceled	(116,184)
Stock option activity, shares outstanding, at end of period	4,326,014	3,012,923
Stock option activity, options exercisable at end of period	1,230,409
Stock option activity, options vested and expected to vest at end of period	4,063,224
Weighted average exercise price, options outstanding at beginning of period	$ 16.65
Weighted average exercise price, options granted	27.93
Weighted average exercise price, Option Exercised	5.97
Weighted average exercise price, Option Canceled	27.45
Weighted average exercise price, options outstanding at end of period	20.28	$ 16.65
Weighted average exercise price, options exercisable at end of period	9.20
Weighted average exercise price, Option Vested and expected to vest at the end of period	$ 20.08
Weighted average remaining contractual life outstanding	8 years 7 months 6 days	8 years 8 months 12 days
Weighted average exercise price exercisable	7 years 7 months 6 days
Weighted average exercise price vested and expected to vest	8 years 7 months 13 days
Aggregate intrinsic value outstanding	$ 41,482	$ 64,659
Aggregate intrinsic value exercisable	23,324
Aggregate intrinsic value vested and expected to vest	$ 39,629