CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Transportation	$ 3,102,043	$ 2,713,688
Sourcing	313,082	360,255
Total revenues	3,415,125	3,073,943
Costs and expenses:
Purchased transportation and related services	2,563,885	2,179,622
Purchased products sourced for resale	282,674	330,986
Personnel expenses	290,504	277,497
Other selling, general, and administrative expenses	90,104	86,886
Total costs and expenses	3,227,167	2,874,991
Income from operations	187,958	198,952
Interest and other expense	(9,302)	(8,772)
Income before provision for income taxes	178,656	190,180
Provision for income taxes	56,576	71,217
Net income	122,080	118,963
Other comprehensive income	17,405	3,550
Comprehensive income	$ 139,485	$ 122,513
Basic net income per share (in dollars per share)	$ 0.86	$ 0.83
Diluted net income per share (in dollars per share)	$ 0.86	$ 0.83
Basic weighted average shares outstanding (shares)	141,484	143,525
Dilutive effect of outstanding stock awards (shares)	374	133
Diluted weighted average shares outstanding (shares)	141,858	143,658
Cash dividends declared per common share (in dollars per share)	$ 0.45	$ 0.43