Leases - Schedule of Components of Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating lease	$ 82	$ 81	$ 246	$ 244
Variable lease costs	3	1	10	1
Total lease cost	$ 85	$ 82	$ 256	$ 245