Description of Business and Summary of Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Property and Equipment, Estimated Useful Lives

Depreciation is computed using the straight-line method based on the following service lives:

	Years
Structures	20 to 25
Tractors	6 to 10
Trailers	10 to 14
Other revenue equipment	7 to 14
Technology equipment and software	3 to 5
Other	3 to 10

Schedule of Property and Equipment

At December 31, property and equipment consisted of the following (in thousands):

	2017		2016
Land	$	81,487	$	69,115
Structures		268,723		196,843
Tractors		398,652		350,737
Trailers		305,540		279,393
Other revenue equipment*		77,691		70,113
Technology equipment and software		93,754		80,342
Other*		64,147		55,403
Total property and equipment, at cost	$	1,289,994	$	1,101,946

* Certain reclassifications have been made to the 2016 categories above to conform to current year presentation.

Summary of Risk Retention Amounts Per Occurrence

Risk retention amounts per occurrence during the three years ended December 31, 2017, were as follows:

Workers’ compensation	$	1,000,000
Bodily injury and property damage		2,000,000
Employee medical and hospitalization		400,000
Cargo loss and damage		250,000