Consolidated Statements of Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating revenues, excluding fuel surcharge revenues	$ 5,516,282	$ 5,082,827	$ 4,527,238
Fuel surcharge revenues	671,364	1,082,614	1,057,333
Total operating revenues	6,187,646	6,165,441	5,584,571
Operating expenses:
Rents and purchased transportation	2,994,586	3,085,276	2,805,568
Salaries, wages and employee benefits	1,394,239	1,290,404	1,138,213
Fuel and fuel taxes	313,034	453,919	455,926
Depreciation and amortization	339,613	294,496	253,380
Operating supplies and expenses	220,597	218,539	202,700
Insurance and claims	73,689	81,062	55,158
General and administrative expenses, net of asset dispositions	72,522	50,596	45,469
Operating taxes and licenses	43,084	38,796	32,307
Communication and utilities	20,588	20,811	19,142
Total operating expenses	5,471,952	5,533,899	5,007,863
Operating income	715,694	631,542	576,708
Interest income	86	87	69
Interest expense	25,577	27,028	23,209
Earnings before income taxes	690,203	604,601	553,568
Income taxes	262,968	229,809	211,186
Net earnings	$ 427,235	$ 374,792	$ 342,382
Weighted average basic shares outstanding (in shares)	115,677	117,000	117,449
Basic earnings per share (in dollars per share)	$ 3.69	$ 3.20	$ 2.92
Weighted average diluted shares outstanding (in shares)	116,728	118,445	119,404
Diluted earnings per share (in dollars per share)	$ 3.66	$ 3.16	$ 2.87
Dividends declared per common share (in dollars per share)	$ 0.84	$ 0.80	$ 0.45