Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Cash and cash equivalents	$ 76,393	$ 78,708	$ 88,812	$ 126,184
Accumulated deficit	$ (252,664)	$ (194,175)