Summarizes the Allocation of Total Consideration to the Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Jul. 01, 2017
Business Acquisition [Line Items]
Goodwill	$ 348,161	$ 348,661
Estenson Logistics, LLC [Member]
Business Acquisition [Line Items]
Cash and cash equivalents			$ 12
Accounts receivable trade			26,909
Accounts receivable other			165
Prepaid expenses and other current assets			1,500
Property and equipment			128,477
Other intangibles			66,400
Goodwill			86,059
Other assets			64
Total assets acquired			309,586
Accounts payable trade			4,110
Accrued payroll			5,727
Accrued other			15,058
Equipment debt			112,962
Total liabilities assumed			137,857
Total consideration			$ 171,729