Stock-Based Compensation - Summary of Option Activity (Detail) - 2006 Plan and 2016 Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Beginning balance (in shares)	4,495,145	4,369,042	4,719,784
Granted (in shares)	627,500	687,500	567,500
Forfeited (in shares)	(225,000)	(53)	(232,527)
Expired (in shares)	(557,604)	(15,000)
Exercised (in shares)	(733,223)	(546,344)	(685,715)
Ending balance (in shares)	3,606,818	4,495,145	4,369,042	4,719,784
Exercisable at end of period (in shares)	2,556,394
Vested and expected to vest at end of period (in shares)	3,482,804
Weighted Average Exercise Price at Grant Date
Beginning balance (in dollars per share)	$ 12.21	$ 11.15	$ 10.03
Granted (in dollars per share)	11.27	18.38	19.22
Forfeited (in dollars per share)	18.83	7.94	13.99
Expired (in dollars per share)	14.21	14.78
Exercised (in dollars per share)	7.68	11.47	9.12
Ending balance (in dollars per share)	12.24	$ 12.21	$ 11.15	$ 10.03
Exercisable at end of period (in dollars per share)	11.52
Vested and expected to vest at end of period (in dollars per share)	$ 12.22
Weighted Average Remaining Term (Years)
Weighted Average Remaining Term	5 years 9 months 3 days	5 years 6 months 29 days	5 years 3 months 10 days	5 years 7 months 17 days
Exercisable at end of period	4 years 6 months 10 days
Vested and expected to vest at end of period	5 years 7 months 20 days
Aggregate Intrinsic Value
Beginning balance	$ 22,148	$ 65,438	$ 24,421
Exercised	2,868	2,482	5,945
Ending balance	8,511	$ 22,148	$ 65,438	$ 24,421
Exercisable at end of period	7,302
Vested and expected to vest at end of period	$ 8,337

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.