Equity Incentive Plans - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares Outstanding, Beginning Balance	3,423	5,555	7,717
Number of Shares, Granted		75	350
Number of Shares, Exercised	(925)	(966)	(1,042)
Number of Shares, Forfeited or cancelled	(165)	(1,241)	(1,470)
Number of Shares Outstanding, Ending Balance	2,333	3,423	5,555
Number of Shares, Vested and Exercisable	1,717
Number of Shares, Vested and Expected to vest	2,004
Weighted-Average Exercise Price, Beginning Balance	$ 2.35	$ 3.33	$ 4.05
Weighted-Average Exercise Price, Granted		6.45	4.40
Weighted-Average Exercise Price, Exercised	2.36	2.23	1.77
Weighted-Average Exercise Price, Forfeited or cancelled	3.61	7.07	8.53
Weighted-Average Exercise Price, Ending Balance	2.26	$ 2.35	$ 3.33
Weighted-Average Exercise Price, Vested and Exercisable	2.09
Weighted-Average Exercise Price, Vested and Expected to Vest	$ 2.25
Weighted-Average Remaining Contractual Life (Years)	5 years 8 months 9 days
Weighted-Average Remaining Contractual Life (Years), Vested and Exercisable	5 years 4 months 13 days
Weighted-Average Remaining Contractual Life (Years), Vested and Expected to Vest	6 years 7 days
Aggregate Intrinsic Value, Exercised	$ 4,278	$ 4,954	$ 5,036
Aggregate Intrinsic Value, Outstanding	11,061	$ 18,341	$ 19,015
Aggregate Intrinsic Value, Vested and Exercisable	8,440
Aggregate Intrinsic Value, Vested and Expected to Vest	$ 9,527