Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income	$ 62,190	$ 79,404
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	136,507	122,196
Deferred income taxes	(2,896)	1,088
Gain on disposal of property and equipment	(3,411)	(10,383)
Non-cash equity compensation	3,544	4,365
Insurance and claims accruals, net of current portion	6,601	11,967
Other	11,036	(3,365)
Changes in certain working capital items:
Accounts receivable, net	23,463	6,688
Other current assets	14,515	7,028
Accounts payable	(1,323)	5,554
Other current liabilities	37,116	(4,206)
Net cash provided by operating activities	287,342	220,336
Cash flows from investing activities:
Additions to property and equipment	(170,235)	(239,289)
Proceeds from sales of property and equipment	62,626	76,936
Decrease in notes receivable	4,392	6,505
Net cash used in investing activities	(103,217)	(155,848)
Cash flows from financing activities:
Repayments of short-term debt	(75,000)	0
Repayments of long-term debt	(50,000)	0
Proceeds from issuance of long-term debt	0	265,000
Dividends on common stock	(12,450)	(273,734)
Repurchases of common stock	(8,798)	(42,301)
Tax withholding related to net share settlements of restricted stock awards	(3,935)	(1,189)
Net cash used in financing activities	(150,183)	(52,224)
Effect of exchange rate fluctuations on cash	(1,995)	226
Net increase in cash, cash equivalents and restricted cash	31,947	12,490
Cash, cash equivalents and restricted cash, beginning of period	33,442	33,930
Cash, cash equivalents and restricted cash, end of period	65,389	46,420
Supplemental disclosures of cash flow information:
Interest paid	2,996	1,830
Income taxes paid	2,992	36,805
Supplemental schedule of non-cash investing and financing activities:
Notes receivable issued upon sale of property and equipment	1,429	3,732
Change in fair value of interest rate swaps	(6,220)	(211)
Property and equipment acquired included in accounts payable	12,090	6,126
Property and equipment disposed included in other receivables	1,982	0
Dividends accrued but not yet paid at end of period	$ 6,219	$ 6,227