Goodwill and Intangibles - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	$ 152	$ 513
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