Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net earnings	$ 728,287	$ 969,351	$ 760,806
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	737,954	644,520	557,093
Noncash lease expense	97,666	83,797	55,137
Share-based compensation	79,189	77,535	61,505
(Gain)/loss on sale of revenue equipment and other	27,806	(25,422)	5,540
Deferred income taxes	15,677	175,089	53,420
Changes in operating assets and liabilities:
Trade accounts receivable	259,449	(13,950)	(382,216)
Income taxes receivable or payable	62,054	(69,025)	(30,633)
Other current assets	(39,351)	(83,892)	(15,252)
Trade accounts payable	(48,346)	(23,838)	140,295
Claims accruals	18,429	117,887	35,051
Accrued payroll and other accrued expenses	(194,196)	(75,170)	(16,848)
Net cash provided by operating activities	1,744,618	1,776,882	1,223,898
Cash flows from investing activities:
Additions to property and equipment	(1,862,431)	(1,540,796)	(947,563)
Proceeds from sale of equipment	262,216	108,901	70,545
Business acquisitions	(85,000)	(118,175)	0
Net cash used in investing activities	(1,685,215)	(1,550,070)	(877,018)
Cash flows from financing activities:
Payments on long-term debt	0	(350,000)	0
Proceeds from revolving lines of credit and other	2,223,600	1,738,100	0
Payments on revolving lines of credit and other	(1,911,100)	(1,420,600)	0
Purchase of treasury stock	(159,576)	(300,030)	(151,720)
Stock repurchased for payroll taxes and other	(37,012)	(31,180)	(28,471)
Dividends paid	(173,898)	(166,724)	(124,442)
Net cash used in financing activities	(57,986)	(530,434)	(304,633)
Net (decrease)/increase in cash and cash equivalents	1,417	(303,622)	42,247
Cash and cash equivalents at beginning of year	51,927	355,549	313,302
Cash and cash equivalents at end of year	53,344	51,927	355,549
Supplemental disclosure of cash flow information:
Interest	65,561	50,433	47,016
Income taxes	135,385	195,827	203,740
Noncash investing activities
Accruals for equipment received	$ 44,692	$ 107,474	$ 60,464