Commitments and Contingencies - Additional Information (Detail)		3 Months Ended		9 Months Ended
	Mar. 01, 2018 USD ($) ft²	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Commitment And Contingencies [Line Items]
Long-term lease agreement, area of office space | ft²	19,275
Lease term	11 years
Total lease payments	$ 7,300,000	$ 116,000	$ 114,000	$ 343,000	$ 336,000
Lessee, operating lease, existence of option to extend	true
Renewal term	5 years
Renewal term, description				The Company has the option to renew for two consecutive five-year periods from the end of the first term and the Company is not reasonably certain that the option to renew the Lease will be exercised. Under the Lease, the Company furnished a security deposit in the form of a standby letter of credit in the amount of $0.3 million, which was reduced by fifty-five thousand dollars on the first anniversary of the commencement date.  The security deposit will continue to be reduced by fifty-five thousand dollars every two years on the commencement date anniversary for eight years.
Security deposit in the form of a standby letter of credit	$ 300,000
Decrease in security deposit	$ 55,000
Maximum
Commitment And Contingencies [Line Items]
Milestone payments from the Company				$ 19,000,000.0