Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net earnings	$ 969,351	$ 760,806	$ 506,035
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	644,520	557,093	527,375
Noncash lease expense	83,797	55,137	45,985
Share-based compensation	77,535	61,505	60,698
(Gain)/loss on sale of revenue equipment and other	(25,422)	5,540	4,389
Deferred income taxes	175,089	53,420	(7,056)
Changes in operating assets and liabilities:
Trade accounts receivable	(13,950)	(382,216)	(109,758)
Income taxes receivable or payable	(69,025)	(30,633)	57,851
Other current assets	(83,892)	(15,252)	(18,038)
Trade accounts payable	(23,838)	140,295	(5,482)
Claims accruals	117,887	35,051	(9,072)
Accrued payroll and other accrued expenses	(75,170)	(16,848)	69,932
Net cash provided by operating activities	1,776,882	1,223,898	1,122,859
Cash flows from investing activities:
Additions to property and equipment	(1,540,796)	(947,563)	(738,545)
Proceeds from sale of equipment	108,901	70,545	137,776
Business acquisition	(118,175)	0	(12,136)
Change in other assets	0	0	(52)
Net cash used in investing activities	(1,550,070)	(877,018)	(612,957)
Cash flows from financing activities:
Payments on long-term debt	(350,000)	0	0
Proceeds from revolving lines of credit and other	1,738,100	0	222,124
Payments on revolving lines of credit and other	(1,420,600)	0	(220,100)
Purchase of treasury stock	(300,030)	(151,720)	(92,548)
Stock repurchased for payroll taxes and other	(31,180)	(28,471)	(26,842)
Dividends paid	(166,724)	(124,442)	(114,234)
Net cash used in financing activities	(530,434)	(304,633)	(231,600)
Net (decrease)/increase in cash and cash equivalents	(303,622)	42,247	278,302
Cash and cash equivalents at beginning of year	355,549	313,302	35,000
Cash and cash equivalents at end of year	51,927	355,549	313,302
Supplemental disclosure of cash flow information:
Interest	50,433	47,016	48,351
Income taxes	195,827	203,740	95,454
Noncash investing activities
Accruals for equipment received	$ 107,474	$ 60,464	$ 12,533