Equity Incentive Plans - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares Outstanding, Beginning Balance	1,115	1,328	2,333
Number of Shares, Exercised	(49)	(177)	(915)
Number of Shares, Forfeited or cancelled	(122)	(36)	(90)
Number of Shares Outstanding, Ending Balance	944	1,115	1,328
Number of Shares, Vested and Exercisable	944
Weighted-Average Exercise Price, Beginning Balance	$ 2.45	$ 2.50	$ 2.26
Weighted-Average Exercise Price, Exercised	1.75	2.42	1.89
Weighted-Average Exercise Price, Forfeited or cancelled	4.65	4.40	2.48
Weighted-Average Exercise Price, Ending Balance	2.20	$ 2.45	$ 2.50
Weighted-Average Exercise Price, Vested and Exercisable	$ 2.20
Weighted-Average Remaining Contractual Life (Years)	2 years 7 months 28 days
Weighted-Average Remaining Contractual Life (Years), Vested and Exercisable	2 years 7 months 28 days
Aggregate Intrinsic Value, Exercised	$ 70	$ 407	$ 3,689
Aggregate Intrinsic Value, Outstanding	627	$ 970	$ 6,175
Aggregate Intrinsic Value, Vested and Exercisable	$ 627