Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net earnings	$ 253,234	$ 269,794
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	243,924	213,006
Noncash lease expense	18,230	0
Share-based compensation	28,304	26,001
Loss on sale of revenue equipment and other	5,042	6,459
Deferred income taxes	32,601	10,996
Changes in operating assets and liabilities:
Trade accounts receivable	20,512	(98,855)
Other assets	(23,403)	(26,693)
Trade accounts payable	33,015	33,716
Income taxes payable or receivable	34,931	54,392
Claims accruals	783	12,150
Accrued payroll and other accrued expenses	(40,512)	28,067
Net cash provided by operating activities	606,661	529,033
Cash flows from investing activities:
Additions to property and equipment	(555,131)	(411,744)
Net proceeds from sale of equipment	79,800	57,613
Business acquisition	(98,543)	0
Changes in other assets	(45)	(1,293)
Net cash used in investing activities	(573,919)	(355,424)
Cash flows from financing activities:
Proceeds from issuances of long-term debt	700,000	0
Payments on long-term debt	(250,000)	0
Proceeds from revolving lines of credit and other	1,334,499	1,421,328
Payments on revolving lines of credit and other	(1,570,400)	(1,492,600)
Purchase of treasury stock	(189,734)	(50,027)
Stock repurchased for payroll taxes and other	(1,554)	852
Dividends paid	(56,278)	(52,583)
Net cash used in financing activities	(33,467)	(173,030)
Net change in cash and cash equivalents	(725)	579
Cash and cash equivalents at beginning of period	7,600	14,612
Cash and cash equivalents at end of period	6,875	15,191
Supplemental disclosure of cash flow information:
Interest	20,046	19,027
Income taxes	15,794	27,762
Noncash investing activities
Accruals for equipment received	$ 47,920	$ 56,645