CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Transportation	$ 11,989,780	$ 11,936,512	$ 11,082,942
Sourcing	1,486,304	1,533,555	1,669,134
Total revenues	13,476,084	13,470,067	12,752,076
Costs and expenses:
Purchased transportation and related services	9,842,271	10,044,406	9,373,797
Purchased products sourced for resale	1,365,333	1,418,009	1,542,184
Personnel expenses	1,051,410	939,021	826,661
Other selling, general, and administrative expenses	358,760	320,213	326,784
Total costs and expenses	12,617,774	12,721,649	12,069,426
Income from operations	858,310	748,418	682,650
Interest and other expense	(35,529)	(24,987)	(9,289)
Income before provision for income taxes	822,781	723,431	673,361
Provision for income taxes	313,082	273,720	257,457
Net income	509,699	449,711	415,904
Other comprehensive loss	(9,336)	(17,990)	(1,275)
Comprehensive income	$ 500,363	$ 431,721	$ 414,629
Basic net income per share (in dollars per share)	$ 3.52	$ 3.06	$ 2.65
Diluted net income per share (in dollars per share)	$ 3.51	$ 3.05	$ 2.65
Basic weighted average shares outstanding (in shares)	144,967	147,202	156,915
Dilutive effect of outstanding stock awards (in shares)	382	340	165
Diluted weighted average shares outstanding (in shares)	145,349	147,542	157,080