Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 23,058	$ 36,086
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	68,837	60,759
Deferred income taxes	(2,912)	425
Gain on disposal of property and equipment	(2,469)	(5,929)
Non-cash equity compensation	2,406	2,051
Insurance and claims accruals, net of current portion	5,973	5,940
Other	88	(2,748)
Changes in certain working capital items:
Accounts receivable, net	11,946	24,403
Other current assets	12,195	6,216
Accounts payable	354	3,642
Other current liabilities	13,900	7,924
Net cash provided by operating activities	133,376	138,769
Cash flows from investing activities:
Additions to property and equipment	(57,231)	(120,357)
Proceeds from sales of property and equipment	38,391	36,993
Decrease in notes receivable	2,316	3,426
Net cash used in investing activities	(16,524)	(79,938)
Cash flows from financing activities:
Repayments of long-term debt	(50,000)	0
Dividends on common stock	(6,232)	(6,340)
Repurchases of common stock	(8,798)	(20,545)
Tax withholding related to net share settlements of restricted stock awards	(3,930)	(1,179)
Net cash used in financing activities	(68,960)	(28,064)
Effect of exchange rate fluctuations on cash	(2,073)	45
Net increase in cash, cash equivalents and restricted cash	45,819	30,812
Cash, cash equivalents and restricted cash, beginning of period	33,442	33,930
Cash, cash equivalents and restricted cash, end of period	79,261	64,742
Supplemental disclosures of cash flow information:
Interest paid	1,811	864
Income taxes paid	611	556
Supplemental schedule of non-cash investing and financing activities:
Notes receivable issued upon sale of property and equipment	1,099	2,092
Change in fair value of interest rate swaps	(5,597)	(105)
Property and equipment acquired included in accounts payable	13,848	15,050
Property and equipment disposed included in other receivables	1,251	72
Dividends accrued but not yet paid at end of period	6,218	6,290
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	72,237	64,742
Restricted cash included in other current assets	7,024	0
Cash, cash equivalents and restricted cash, end of period	$ 79,261	$ 64,742