Prepaid Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid expenses	$ 6,258	$ 12,076
Prepaid R&D clinical costs	4,098	11,286
Prepaid insurance	855	223
Other prepaid costs	$ 1,305	$ 567