Long-Term Debt - Summary of Long Term Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Principal amount of long-term debt	$ 32,500	$ 32,500
Debt discount, net of accretion	266	223
Cumulative accretion of end of term payments	970	455
Long-term debt	33,736	33,178
Current portion of long-term debt	(693)	0
Long-term debt, net of current portion	$ 33,043	$ 33,178