Goodwill and Intangibles - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	$ 49	$ 47
Minimum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	2 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	10 years