Description of Business and Summary of Accounting Policies - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 1,289,994	$ 1,101,946
Land [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	81,487	69,115
Structures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	268,723	196,843
Tractors [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	398,652	350,737
Trailers [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	305,540	279,393
Other Revenue Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	77,691	70,113
Technology Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	93,754	80,342
Other [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 64,147	$ 55,403