Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net earnings	$ 570,886	$ 728,287	$ 969,351
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	761,141	737,954	644,520
Noncash lease expense	100,178	97,666	83,797
Share-based compensation	65,686	79,189	77,535
(Gain)/loss on sale of revenue equipment and other	14,557	27,806	(25,422)
Deferred income taxes	(89,848)	65,566	175,089
Changes in operating assets and liabilities:
Trade accounts receivable	110,746	259,449	(13,950)
Income taxes receivable or payable	(26,182)	12,165	(69,025)
Other current assets	94,639	(39,351)	(83,892)
Trade accounts payable	(109,806)	(48,346)	(23,838)
Claims accruals	48,137	18,429	117,887
Accrued payroll and other accrued expenses	(56,978)	(194,196)	(75,170)
Net cash provided by operating activities	1,483,156	1,744,618	1,776,882
Cash flows from investing activities:
Additions to property and equipment	(865,373)	(1,862,431)	(1,540,796)
Proceeds from sale of equipment	190,967	262,216	108,901
Proceeds from sale of investment	6,929	0	0
Business acquisitions	3,785	(85,000)	(118,175)
Net cash used in investing activities	(663,692)	(1,685,215)	(1,550,070)
Cash flows from financing activities:
Payments on long-term debt	(250,000)	0	(350,000)
Proceeds from revolving lines of credit and other	3,070,600	2,223,600	1,738,100
Payments on revolving lines of credit and other	(2,920,600)	(1,911,100)	(1,420,600)
Purchase of treasury stock	(513,924)	(159,576)	(300,030)
Stock repurchased for payroll taxes and other	(36,358)	(37,012)	(31,180)
Dividends paid	(175,543)	(173,898)	(166,724)
Net cash used in financing activities	(825,825)	(57,986)	(530,434)
Net (decrease)/increase in cash and cash equivalents	(6,361)	1,417	(303,622)
Cash and cash equivalents at beginning of year	53,344	51,927	355,549
Cash and cash equivalents at end of year	46,983	53,344	51,927
Supplemental disclosure of cash flow information:
Interest	80,861	65,561	50,433
Income taxes	305,103	135,385	195,827
Noncash investing activities
Accruals for equipment received	$ 73,906	$ 44,692	$ 107,474