Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Total revenues	$ 3,627,846	$ 3,908,840	$ 7,432,854	$ 7,660,050
Costs and expenses:
Personnel expenses	300,483	338,886	630,703	678,984
Other selling, general, and administrative expenses	125,183	128,795	253,476	242,947
Total costs and expenses	3,439,059	3,681,305	7,134,627	7,207,965
Income from operations	188,787	227,535	298,227	452,085
Interest and other expense	(10,211)	(6,615)	(25,439)	(23,755)
Income before provision for income taxes	178,576	220,920	272,788	428,330
Provision for income taxes	34,637	51,740	50,703	97,362
Net income	143,939	169,180	222,085	330,968
Other comprehensive income (loss), net of tax	24,253	(5,688)	(7,942)	(391)
Comprehensive income	$ 168,192	$ 163,492	$ 214,143	$ 330,577
Basic net income per share (in dollars per share)	$ 1.07	$ 1.23	$ 1.64	$ 2.41
Diluted net income per share (in dollars per share)	$ 1.06	$ 1.22	$ 1.64	$ 2.39
Basic weighted average shares outstanding (shares)	135,010	137,185	135,241	137,518
Dilutive effect of outstanding stock awards (shares)	600	1,071	535	1,149
Diluted weighted average shares outstanding (shares)	135,610	138,256	135,776	138,667
Transportation
Revenues:
Total revenues	$ 3,348,611	$ 3,638,612	$ 6,890,729	$ 7,143,544
Costs and expenses:
Purchased products and services	2,762,590	2,972,998	5,762,703	5,826,254
Sourcing
Revenues:
Total revenues	279,235	270,228	542,125	516,506
Costs and expenses:
Purchased products and services	$ 250,803	$ 240,626	$ 487,745	$ 459,780