Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net earnings	$ 498,666	$ 318,768
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	306,334	276,916
Noncash lease expense	39,066	25,411
Share-based compensation	39,584	31,466
(Gain)/loss on sale of revenue equipment and other	(20,667)	2,359
Deferred income taxes	65,189	36,945
Changes in operating assets and liabilities:
Trade accounts receivable	(262,943)	(169,521)
Other assets	61,653	85,657
Trade accounts payable	83,856	49,273
Income taxes payable or receivable	(13,915)	(26,359)
Claims accruals	24,905	7,359
Accrued payroll and other accrued expenses	(37,201)	30,474
Net cash provided by operating activities	784,527	668,748
Cash flows from investing activities:
Additions to property and equipment	(667,742)	(306,727)
Net proceeds from sale of equipment	69,648	46,016
Business acquisition	(86,939)	0
Changes in other assets	0	(88)
Net cash used in investing activities	(685,033)	(260,799)
Cash flows from financing activities:
Proceeds from revolving lines of credit and other	0	1,011
Purchase of treasury stock	(239,340)	(86,580)
Stock repurchased for payroll taxes and other	(8,188)	(3,463)
Dividends paid	(83,674)	(61,301)
Net cash used in financing activities	(331,202)	(150,333)
Net change in cash and cash equivalents	(231,708)	257,616
Cash and cash equivalents at beginning of period	355,549	313,302
Cash and cash equivalents at end of period	123,841	570,918
Supplemental disclosure of cash flow information:
Interest	21,335	24,341
Income taxes	111,641	92,368
Noncash investing activities
Accruals for equipment received	$ 90,490	$ 50,606