Condensed Consolidated Statements of Earnings (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating revenues	$ 3,838,257	$ 3,144,812	$ 11,164,377	$ 8,671,331
Operating expenses:
Rents and purchased transportation	1,891,848	1,667,236	5,650,011	4,557,770
Salaries, wages and employee benefits	887,723	711,694	2,493,139	1,997,196
Fuel and fuel taxes	242,379	139,155	697,481	379,036
Depreciation and amortization	166,580	138,923	472,914	415,839
Operating supplies and expenses	138,346	98,541	371,668	271,257
Insurance and claims	60,189	41,254	193,577	114,792
General and administrative expenses, net of asset dispositions	62,815	50,266	160,026	142,662
Operating taxes and licenses	17,082	15,464	49,154	43,488
Communication and utilities	9,067	8,450	26,802	26,264
Total operating expenses	3,476,029	2,870,983	10,114,772	7,948,304
Operating income	362,228	273,829	1,049,605	723,027
Net interest expense	13,562	11,977	38,991	36,061
Earnings before income taxes	348,666	261,852	1,010,614	686,966
Income taxes	79,284	62,023	242,566	168,369
Net earnings	$ 269,382	$ 199,829	$ 768,048	$ 518,597
Weighted average basic shares outstanding (in shares)	103,757	105,173	104,297	105,452
Basic earnings per share (in dollars per share)	$ 2.60	$ 1.90	$ 7.36	$ 4.92
Weighted average diluted shares outstanding (in shares)	104,924	106,436	105,458	106,688
Diluted earnings per share (in dollars per share)	$ 2.57	$ 1.88	$ 7.28	$ 4.86
Service Excluding Fuel Surcharge [Member]
Operating revenues	$ 3,162,106	$ 2,813,939	$ 9,364,082	$ 7,808,954
Fuel Surcharge [Member]
Operating revenues	$ 676,151	$ 330,873	$ 1,800,295	$ 862,377