Leases - Information related to Right-of-use Assets and Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Cash paid for operating lease liabilities	$ 62	$ 87	$ 185	$ 417
Right-of-use assets obtained in exchange for new operating lease obligations	$ 0	$ 1,440	$ 48	$ 2,037
Weighted-average remaining lease term	3 years 9 months 18 days	4 years 10 months 24 days	3 years 9 months 18 days	5 years 2 months 12 days
Weighted-average discount rate	12.30%	12.30%	12.30%	12.30%