Condensed Consolidated Statements of Earnings (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating revenues	$ 3,488,588	$ 2,618,149
Operating expenses:
Rents and purchased transportation	1,837,340	1,352,301
Salaries, wages and employee benefits	763,591	620,032
Fuel and fuel taxes	189,466	113,040
Depreciation and amortization	148,763	137,545
Operating supplies and expenses	106,939	81,698
General and administrative expenses, net of asset dispositions	37,447	44,891
Insurance and claims	46,131	38,030
Operating taxes and licenses	15,749	13,814
Communication and utilities	8,868	9,146
Total operating expenses	3,154,294	2,410,497
Operating income	334,294	207,652
Net interest expense	12,586	12,024
Earnings before income taxes	321,708	195,628
Income taxes	78,383	49,022
Net earnings	$ 243,325	$ 146,606
Weighted average basic shares outstanding (in shares)	104,894	105,678
Basic earnings per share (in dollars per share)	$ 2.32	$ 1.39
Weighted average diluted shares outstanding (in shares)	106,075	106,816
Diluted earnings per share (in dollars per share)	$ 2.29	$ 1.37
Service Excluding Fuel Surcharge [Member]
Operating revenues	$ 3,042,217	$ 2,388,034
Fuel Surcharge [Member]
Operating revenues	$ 446,371	$ 230,115