Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net earnings	$ 119,601	$ 118,142
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	119,930	105,583
Noncash lease expense	8,484
Share-based compensation	13,571	12,036
Loss on sale of revenue equipment and other	2,252	2,815
Deferred income taxes	25,030	3,412
Changes in operating assets and liabilities:
Trade accounts receivable	58,109	19,864
Other assets	(54,421)	(49,189)
Trade accounts payable	(14,325)	(10,650)
Income taxes payable or receivable	12,213	35,434
Claims accruals	(920)	12,543
Accrued payroll and other accrued expenses	(38,783)	11,628
Net cash provided by operating activities	250,741	261,618
Cash flows from investing activities:
Additions to property and equipment	(257,658)	(206,108)
Net proceeds from sale of equipment	45,512	27,063
Business acquisition	(98,543)
Change in other assets	(15)	(299)
Net cash used in investing activities	(310,704)	(179,344)
Cash flows from financing activities:
Proceeds from issuances of long-term debt	700,000
Payments on long-term debt	(250,000)
Proceeds from revolving lines of credit and other	730,618	687,036
Payments on revolving lines of credit and other	(1,045,100)	(750,400)
Stock repurchased for payroll taxes	(2,520)	(99)
Dividends paid	(28,272)	(26,341)
Net cash provided by/(used in) financing activities	104,726	(89,804)
Net change in cash and cash equivalents	44,763	(7,530)
Cash and cash equivalents at beginning of period	7,600	14,612
Cash and cash equivalents at end of period	52,363	7,082
Supplemental disclosure of cash flow information:
Interest	14,363	11,769
Income taxes	2,163	1,834
Noncash investing activities
Accruals for equipment received	$ 49,639	$ 42,554