Condensed Consolidated Statements of Earnings (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Operating revenues	$ 2,928,685	$ 3,132,623	$ 5,872,685	$ 6,362,212
Operating expenses:
Rents and purchased transportation	1,274,011	1,404,586	2,554,998	2,872,384
Salaries, wages and employee benefits	803,047	821,876	1,610,931	1,646,875
Depreciation and amortization	184,658	179,972	367,655	355,784
Fuel and fuel taxes	164,291	171,846	337,817	367,680
Operating supplies and expenses	120,425	128,949	243,416	257,308
General and administrative expenses, net of asset dispositions	74,707	61,472	151,490	121,879
Insurance and claims	73,222	63,893	148,908	134,221
Operating taxes and licenses	17,575	18,951	35,110	37,058
Communication and utilities	11,040	10,366	22,282	20,822
Total operating expenses	2,722,976	2,861,911	5,472,607	5,814,011
Operating income	205,709	270,712	400,078	548,201
Net interest expense	20,198	14,604	35,847	29,393
Earnings before income taxes	185,511	256,108	364,231	518,808
Income taxes	49,638	66,556	100,865	131,488
Net earnings	$ 135,873	$ 189,552	$ 263,366	$ 387,320
Weighted average basic shares outstanding (in shares)	102,386	103,562	102,814	103,643
Basic earnings per share (in dollars per share)	$ 1.33	$ 1.83	$ 2.56	$ 3.74
Weighted average diluted shares outstanding (in shares)	103,146	104,566	103,626	104,647
Diluted earnings per share (in dollars per share)	$ 1.32	$ 1.81	$ 2.54	$ 3.7
Service Excluding Fuel Surcharge [Member]
Operating revenues	$ 2,545,023	$ 2,707,560	$ 5,097,508	$ 5,450,070
Fuel Surcharge [Member]
Operating revenues	$ 383,662	$ 425,063	$ 775,177	$ 912,142