Leases - Summary of Maturity of Lease Liabilities (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Leases [Abstract]
Remainder of 2019	$ 733
2020	4,173
2021	4,628
2022	4,713
2023	1,188
Total lease payments	15,435
Less imputed interests	(2,405)
Total lease liabilities	$ 13,030