Stock-Based Compensation - Summary of Option Activity for 2006 Plan and the 2016 Plan (Detail) - 2006 Plan and 2016 Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Beginning balance (in shares)	4,369,042	4,719,784	5,548,336
Granted (in shares)	687,500	567,500	643,000
Forfeited (in shares)	(53)	(232,527)	(290,729)
Expired (in shares)	(15,000)		(605,617)
Exercised (in shares)	(546,344)	(685,715)	(575,206)
Ending balance (in shares)	4,495,145	4,369,042	4,719,784	5,548,336
Exercisable (in shares)	3,371,836
Vested and expected to vest at end of period (in shares)	4,354,708
Weighted Average Exercise Price at Grant Date
Beginning balance (in dollars per share)	$ 11.15	$ 10.03	$ 11.62
Granted (in dollars per share)	18.38	19.22	14.44
Forfeited (in dollars per share)	7.94	13.99	10.73
Expired (in dollars per share)	14.78		29.87
Exercised (in dollars per share)	11.47	9.12	9.13
Ending balance (in dollars per share)	12.21	$ 11.15	$ 10.03	$ 11.62
Exercisable (in dollars per share)	10.31
Vested and expected to vest at end of period (in dollars per share)	$ 12.02
Weighted Average Remaining Term (Years)
Weighted Average Remaining Term	5 years 6 months 29 days	5 years 3 months 10 days	5 years 7 months 17 days	5 years 6 months 29 days
Exercisable	4 years 6 months 10 days
Vested and expected to vest at end of period	5 years 5 months 15 days
Aggregate Intrinsic Value
Beginning balance	$ 65,438	$ 24,421	$ 32,453
Exercised	2,482	5,945	3,140
Ending balance	22,148	$ 65,438	$ 24,421	$ 32,453
Exercisable	21,200
Vested and expected to vest at end of period	$ 22,039