Stock-based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
NUMBER OF SHARES
Options outstanding at December 31, 2014	3,826,459
Granted	1,081,000
Exercised	(287,193)
Canceled	(255,323)
Options outstanding at September 30, 2015	4,364,943
Options exercisable at September 30, 2015	2,006,263
WEIGHTED AVERAGE EXERCISE PRICE
Options outstanding at December 31, 2014 (in USD per share)	$ 8.39
Granted (in USD per share)	25.50
Exercised (in USD per share)	4.49
Cancelled (in USD per share)	17.11
Options outstanding at September 30, 2015 (in USD per share)	12.33
Options exercisable at September 30, 2015 (in USD per share)	$ 7.27
AGGREGATE INTRINSIC VALUE
Options outstanding	$ 23,614	$ 79,792
Options exercisable at September 30, 2015	$ 21,006