Stock-based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
NUMBER OF SHARES
Options outstanding at December 31, 2014	3,826,459
Granted	921,400
Exercised	(83,270)
Canceled	(62,758)
Options outstanding at June 30, 2015	4,601,831
Options exercisable at June 30, 2015	1,962,997
WEIGHTED AVERAGE EXERCISE PRICE
Options outstanding at December 31, 2014 (in USD per share)	$ 8.39
Granted (in USD per share)	27.09
Exercised (in USD per share)	1.46
Cancelled (in USD per share)	13.66
Options outstanding at June 30, 2015 (in USD per share)	12.14
Options exercisable at June 30, 2015 (in USD per share)	$ 6.45
AGGREGATE INTRINSIC VALUE
Options outstanding	$ 25,356	$ 79,792
Options exercisable at June 30, 2015	$ 21,986