Goodwill and Other Intangible Assets - Schedule of Carrying Value and Accumulated Amortization of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 7,933	$ 4,552
Accumulated Amortization	3,247	2,709
Customer list
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,393	4,012
Accumulated Amortization	2,880	2,379
Non-Compete Agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	270	270
Accumulated Amortization	175	146
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	270	270
Accumulated Amortization	$ 192	$ 184