Consolidated Statements of Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating revenues	$ 12,168,302	$ 9,636,573	$ 9,165,258
Operating expenses:
Rents and purchased transportation	6,449,068	4,954,123	4,528,812
Salaries, wages and employee benefits	2,761,680	2,347,716	2,167,851
Depreciation and amortization	557,093	527,375	499,145
Fuel and fuel taxes	530,642	357,483	463,195
Operating supplies and expenses	369,294	334,350	333,113
General and administrative expenses, net of asset dispositions	195,616	180,083	191,933
Insurance and claims	165,052	134,482	157,251
Operating taxes and licenses	59,462	54,331	55,336
Communication and utilities	34,865	33,511	34,797
Total operating expenses	11,122,772	8,923,454	8,431,433
Operating income	1,045,530	713,119	733,825
Interest income	493	486	1,754
Interest expense	46,251	47,580	54,684
Earnings before income taxes	999,772	666,025	680,895
Income taxes	238,966	159,990	164,575
Net earnings	$ 760,806	$ 506,035	$ 516,320
Weighted average basic shares outstanding (in shares)	105,359	105,700	107,329
Basic earnings per share (in dollars per share)	$ 7.22	$ 4.79	$ 4.81
Weighted average diluted shares outstanding (in shares)	106,593	106,766	108,307
Diluted earnings per share (in dollars per share)	$ 7.14	$ 4.74	$ 4.77
Service Excluding Fuel Surcharge [Member]
Operating revenues	$ 10,915,442	$ 8,879,653	$ 8,122,600
Fuel Surcharge [Member]
Operating revenues	$ 1,252,860	$ 756,920	$ 1,042,658