Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 183,613	$ 108,522
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	196,431	199,487
Deferred income taxes	14,756	(2,358)
Gain on disposal of property and equipment	(39,292)	(7,293)
Non-cash equity compensation	7,999	6,003
Insurance and claims accruals, net of current portion	2,362	6,579
Other	(1,422)	21,771
Gain on investments in equity securities, net	(36,281)	0
Changes in certain working capital items:
Accounts receivable, net	(69,072)	(15,051)
Other current assets	(10,319)	(1,335)
Accounts payable	17,236	6,477
Other current liabilities	(12,667)	23,594
Net cash provided by operating activities	253,344	346,396
Cash flows from investing activities:
Additions to property and equipment	(295,485)	(294,448)
Proceeds from sales of property and equipment	132,755	107,185
Net cash invested in acquisition	(141,291)	0
Investment in equity securities	(10,000)	0
Decrease in notes receivable	5,114	6,277
Net cash used in investing activities	(308,907)	(180,986)
Cash flows from financing activities:
Repayments of short-term debt	(25,000)	(75,000)
Proceeds from issuance of short-term debt	5,000	0
Repayments of long-term debt	0	(50,000)
Proceeds from issuance of long-term debt	170,000	0
Dividends on common stock	(21,057)	(18,669)
Repurchases of common stock	(53,266)	(8,798)
Tax withholding related to net share settlements of restricted stock awards	(3,773)	(3,941)
Other cash flows from financing activities	(35)	0
Net cash provided by (used in) financing activities	71,869	(156,408)
Effect of exchange rate fluctuations on cash	(212)	(1,968)
Net increase in cash, cash equivalents and restricted cash	16,094	7,034
Cash, cash equivalents and restricted cash, beginning of period	29,334	33,442
Cash, cash equivalents and restricted cash, end of period	45,428	40,476
Supplemental disclosures of cash flow information:
Interest paid	2,517	3,882
Income taxes paid	56,350	36,880
Supplemental schedule of non-cash investing and financing activities:
Notes receivable issued upon sale of property and equipment	4,252	2,283
Change in fair value of interest rate swaps	2,063	(5,819)
Property and equipment acquired included in accounts payable	3,666	24,068
Property and equipment disposed included in other receivables	0	5,183
Dividends accrued but not yet paid at end of period	8,026	6,219
Redeemable noncontrolling interest associated with acquisition	$ 35,322	$ 0