Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net income	$ 55,035	$ 46,492
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	67,229	63,951
Deferred income taxes	(254)	3,487
Gain on disposal of property and equipment	(20,458)	(10,520)
Non-cash equity compensation	3,026	2,502
Insurance and claims accruals, net of current portion	4,470	4,212
Other	(2,080)	1,285
Loss on investments in equity securities	9,806	0
Changes in certain working capital items:
Accounts receivable, net	11,279	(6,798)
Other current assets	13,152	551
Accounts payable	12,330	18,481
Other current liabilities	1,422	12,224
Net cash provided by operating activities	154,957	135,867
Cash flows from investing activities:
Additions to property and equipment	(73,629)	(82,555)
Proceeds from sales of property and equipment	36,555	44,689
Net cash invested in acquisition	705	0
Investment in equity securities	0	(5,000)
Decrease in notes receivable	1,831	1,575
Net cash used in investing activities	(34,538)	(41,291)
Cash flows from financing activities:
Repayments of short-term debt	(1,250)	(25,000)
Repayments of long-term debt	(100,000)	0
Proceeds from issuance of long-term debt	100,000	0
Dividends on common stock	(7,895)	(6,114)
Repurchases of common stock	(36,180)	(5,507)
Tax withholding related to net share settlements of restricted stock awards	(3,658)	(3,740)
Net cash used in financing activities	(48,983)	(40,361)
Effect of exchange rate fluctuations on cash	317	(419)
Net increase in cash and cash equivalents	71,753	53,796
Cash and cash equivalents, beginning of period	54,196	29,334
Cash and cash equivalents, end of period	125,949	83,130
Supplemental disclosures of cash flow information:
Interest paid	1,536	878
Income taxes paid	837	536
Supplemental schedule of non-cash investing and financing activities:
Notes receivable issued upon sale of property and equipment	1,613	988
Change in fair value of interest rate swaps	3,631	1,303
Property and equipment acquired included in accounts payable	13,671	23,570
Property and equipment disposed included in other receivables	154	17
Dividends accrued but not yet paid at end of period	$ 7,807	$ 6,792