Goodwill and Other Intangible Assets - Details of Intangible Assets Acquired (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount,Intangible assets	$ 4,900
Net carrying amount, Accumulated amortization	(2,042)
Intantible assets, net	2,858
Customer Backlog [Member]
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount,Intangible assets	4,000
Net carrying amount, Accumulated amortization	$ (1,666)
Amortization period	12 months
Trade Names and Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount,Intangible assets	$ 900
Amortization period	12 months
Trade Name [Member]
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount, Accumulated amortization	$ (376)