Commitments and Contingencies - Summary of Future Minimum Payments under Operating Lease (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 474
2020	1,933
2021	1,989
2022	2,046
2023	689
Total future minimum lease payments	7,131
Less: imputed interest	719
Total operating lease liability	6,412
Current operating lease liability	1,581
Operating lease liability, net of current portion	4,831
Total operating lease liability	$ 6,412