Commitments and Contingencies - Schedule of Components of Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Operating lease cost	$ 76	$ 108	$ 229	$ 340
Sublease income		(43)		(173)
Total operating lease cost	76	65	229	167
Amortization of right-of-use assets	2	1	7	1
Interest on lease liabilities			1
Total finance lease cost	$ 2	$ 1	$ 8	$ 1