Goodwill and Intangible Assets - Classes of Intangible Assets (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Cost	$ 84,000	$ 84,000
Accumulated Amortization	10,386	6,936
Total	$ 73,614	$ 77,064
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period	24 months	24 months
Cost	$ 3,000	$ 3,000
Accumulated Amortization	2,258	1,508
Total	742	1,492
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	81,000	81,000
Accumulated Amortization	8,128	5,428
Total	$ 72,872	$ 75,572
Minimum [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period	156 months	156 months
Maximum [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period	180 months	180 months