Stock-Based Compensation - Compensation Expense by Type of Award (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 3,381	$ 3,063	$ 9,388	$ 7,022
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	2,730	3,005	7,689	6,885
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	603		1,581
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense, total	$ 48	$ 58	$ 118	$ 137