Stock-Based Compensation - Unrecognized Compensation Expense is to be Recognized (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Unrecognized stock based compensation expense	$ 7,201
2016 Employee Stock Purchase Plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Purchase interval period	6 months
Remainder of 2021
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Unrecognized stock based compensation expense	$ 1,022
2022
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Unrecognized stock based compensation expense	2,632
2023
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Unrecognized stock based compensation expense	1,917
2024
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Unrecognized stock based compensation expense	1,158
2025
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Unrecognized stock based compensation expense	$ 472