Commitments and Contingencies - Schedule of Future Minimum Lease Payments under Non-cancellable Operating Leases, Reconciliation of Undiscounted Cash Flows to the Operating Lease Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Operating lease liabilities reported as of December 31, 2020:
Operating lease liabilities - current	$ 1,602	$ 967
Operating lease liabilities - non-current	3,673	$ 3,352
Stamford Operating Lease [Member]
Operating Lease Liabilities, Payments Due [Abstract]
2021	1,921
2022	1,957
2023	1,992
Total future minimum lease payments, undiscounted	5,870
Less imputed interest	(595)
Operating lease liabilities	5,275
Operating lease liabilities reported as of December 31, 2020:
Operating lease liabilities - current	1,602
Operating lease liabilities - non-current	3,673
Total	$ 5,275