Commitments and Contingencies - Elements of Lease Expense (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)		Sep. 30, 2019 USD ($)
Leases, Operating [Abstract]
Operating lease cost	$ 443		$ 1,329
Variable lease cost	254	[1]	835	[1]
Total lease cost	697		$ 2,164
Operating cash flows used for operating leases	$ 2,240
Remaining lease term	3 years 6 months 29 days		3 years 6 months 29 days
Discount rate	6.25%		6.25%

[1] The variable lease costs for the quarter ended September 30, 2019 include common area maintenance and other operating charges.