Stock Incentive Plans - Summary of Options Outstanding Vested and Expected to Vest (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Vested | shares	938,223
Number of Shares, Expected to vest | shares	1,491,586
Number of Shares, Total | shares	2,429,809
Weighted-average Exercise Price, Vested | $ / shares	$ 5.41
Weighted-average Exercise Price, Expected to vest | $ / shares	$ 15.70
Weighted-average Remaining Contractual Life (Years), Vested	6 years 6 months 21 days
Weighted-average Remaining Contractual Life (Years), Expected to vest	9 years 2 months 1 day
Aggregate Intrinsic Value, Vested | $	$ 24,497
Aggregate Intrinsic Value, Expected to vest | $	23,598
Aggregate Intrinsic Value, Total | $	$ 48,095