Stock-Based Compensation - Summary of Activity Under Stock Incentive Plans (Detail) - 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]
Shares Subject to Outstanding, Beginning Balance	3,427,509	3,759,839
Shares Subject to Outstanding, Options granted	1,799,395	352,494
Shares Subject to Outstanding, Options exercised	(228,141)	(609,066)
Shares Subject to Outstanding, Options cancelled and forfeited	(419,981)	(75,758)
Shares Subject to Outstanding, Ending Balance	4,578,782	3,427,509
Shares Subject to Outstanding, Vested and expected to vest	4,561,042
Shares Subject to Outstanding, Exercisable	2,804,796
Weighted-Average Exercise Price Per Share, Outstanding Beginning Balance	$ 3.76	$ 3.00
Weighted-Average Exercise Price Per Share, Options granted	5.17	7.30
Weighted-Average Exercise Price Per Share, Options exercised	1.18	0.59
Weighted-Average Exercise Price Per Share, Options cancelled and forfeited	4.49	7.33
Weighted Average Exercise Price Per Share, Outstanding Ending Balance	4.38	$ 3.76
Weighted Average Exercise Price Per Share, Vested and expected to vest	4.37
Weighted Average Exercise Price Per Share, Exercisable	$ 3.65
Aggregate Intrinsic Value, Outstanding Balance		$ 3,707	$ 12,499