Description of Business and Summary of Accounting Policies - Summary of Property and Equipment, Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2017
Structures [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	20 years
Structures [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	25 years
Tractors [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	6 years
Tractors [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	10 years
Trailers [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	10 years
Trailers [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	14 years
Other Revenue Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	7 years
Other Revenue Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	14 years
Technology Equipment and Software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	3 years
Technology Equipment and Software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	5 years
Other [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	3 years
Other [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	10 years