Stock-Based Compensation - Summary of Option Activity for 2006 Plan and the 2016 Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Number of Shares
Expired (in shares)	(545,104)
Weighted Average Exercise Price at Grant Date
Expired (in dollars per share)	$ 14.29
2006 Plan and 2016 Plan
Number of Shares
Beginning balance (in shares)	4,495,145
Granted (in shares)	537,500
Forfeited (in shares)	(225,000)
Exercised (in shares)	(554,844)
Ending balance (in shares)	3,707,697	4,495,145
Exercisable (in shares)	2,562,003
Vested and expected to vest at end of period (in shares)	3,518,867
Weighted Average Exercise Price at Grant Date
Beginning balance (in dollars per share)	$ 12.21
Granted (in dollars per share)	11.34
Forfeited (in dollars per share)	18.83
Exercised (in dollars per share)	7.35
Ending balance (in dollars per share)	12.10	$ 12.21
Exercisable (in dollars per share)	10.95
Vested and expected to vest at end of period (in dollars per share)	$ 12.03
Weighted Average Remaining Term (Years)
Weighted Average Remaining Term	5 years 10 months 24 days	5 years 6 months 29 days
Exercisable	4 years 6 months 3 days
Vested and expected to vest at end of period	5 years 8 months 15 days
Aggregate Intrinsic Value
Beginning balance	$ 22,148
Exercised	2,113
Ending balance	5,415	$ 22,148
Exercisable	5,317
Vested and expected to vest at end of period	$ 5,395