Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net earnings	$ 127,493	$ 197,768
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	182,996	175,812
Noncash lease expense	26,497	22,852
Share-based compensation	18,409	19,248
Loss on sale of revenue equipment and other	7,271	6,038
Deferred income taxes	16,788	1,446
Changes in operating assets and liabilities:
Trade accounts receivable	62,797	145,179
Other assets	92,021	52,886
Trade accounts payable	(65,398)	(76,106)
Income taxes payable or receivable	27,694	52,951
Claims accruals	5,131	17,085
Accrued payroll and other accrued expenses	(35,232)	(127,538)
Net cash provided by operating activities	466,467	487,621
Cash flows from investing activities:
Additions to property and equipment	(203,387)	(461,314)
Net proceeds from sale of equipment	37,205	81,483
Business acquisition	3,785	0
Net cash used in investing activities	(162,397)	(379,831)
Cash flows from financing activities:
Payments on long-term debt	(250,000)	0
Proceeds from revolving lines of credit and other	407,600	945,400
Payments on revolving lines of credit and other	(367,600)	(966,100)
Purchase of treasury stock	(25,140)	(30,849)
Stock repurchased for payroll taxes and other	(13,671)	(11,980)
Dividends paid	(44,418)	(43,584)
Net cash used in financing activities	(293,229)	(107,113)
Net change in cash and cash equivalents	10,841	677
Cash and cash equivalents at beginning of period	53,344	51,927
Cash and cash equivalents at end of period	64,185	52,604
Supplemental disclosure of cash flow information:
Interest	28,994	24,577
Income taxes	5,351	7,455
Noncash investing activities
Accruals for equipment received	$ 104,467	$ 134,578