Other Assets - Summary of Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Bonds and escrow deposits	$ 628	$ 380
Prepaid insurance	585	486
Other	375	419
Other assets, gross	1,588	1,285
Less : accumulated amortization	(413)	(669)
Other assets	$ 1,175	$ 616