Equity Incentive Plans - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares Outstanding, Beginning Balance	5,555	7,717	8,207
Number of Shares, Granted	75	350	2,815
Number of Shares, Exercised	(966)	(1,042)	(1,683)
Number of Shares, Forfeited or cancelled	(1,241)	(1,470)	(1,622)
Number of Shares Outstanding, Ending Balance	3,423	5,555	7,717
Number of Shares, Vested and Exercisable	1,626
Number of Shares, Vested and Expected to vest	2,868
Weighted-Average Exercise Price, Beginning Balance	$ 3.33	$ 4.05	$ 4.55
Weighted-Average Exercise Price, Granted	6.45	4.40	2.18
Weighted-Average Exercise Price, Exercised	2.23	1.77	1.67
Weighted-Average Exercise Price, Forfeited or cancelled	7.07	8.53	5.70
Weighted-Average Exercise Price, Ending Balance	2.35	$ 3.33	$ 4.05
Weighted-Average Exercise Price, Vested and Exercisable	2.28
Weighted-Average Exercise Price Vested and Expected to Vest	$ 2.37
Weighted-Average Remaining Contractual Life (Years)	6 years 8 months 27 days
Weighted-Average Remaining Contractual Life (Years), Vested and Exercisable	6 years 2 months 1 day
Weighted-Average Remaining Contractual Life (Years), Vested and Expected to Vest	7 years 29 days
Aggregate Intrinsic Value, Exercised	$ 4,954	$ 5,036	$ 4,965
Aggregate Intrinsic Value, Outstanding	18,341	$ 19,015	$ 22,023
Aggregate Intrinsic Value, Vested and Exercisable	8,828
Aggregate Intrinsic Value, Vested and Expected to Vest	$ 15,329