Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 118,448	$ 113,585
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	184,816	170,439
Deferred income taxes	8,413	25,114
Gain on disposal of property and equipment	(14,530)	(15,922)
Non-cash equity compensation	6,346	5,507
Insurance and claims accruals, net of current portion	15,840	21,100
Other	(4,527)	(5,081)
Changes in certain working capital items:
Accounts receivable, net	14,552	(20,737)
Other current assets	5,667	(9,535)
Accounts payable	(532)	11,742
Other current liabilities	(2,308)	6,301
Net cash provided by operating activities	332,185	302,513
Cash flows from investing activities:
Additions to property and equipment	(375,202)	(412,557)
Proceeds from sales of property and equipment	103,543	123,267
Issuance of notes receivable	0	(3,300)
Decrease in notes receivable	9,247	15,846
Net cash used in investing activities	(262,412)	(276,744)
Cash flows from financing activities:
Repayments of short-term debt	0	(40,000)
Proceeds from issuance of short-term debt	0	40,000
Repayments of long-term debt	(50,000)	(20,000)
Proceeds from issuance of long-term debt	275,000	70,000
Change in net checks issued in excess of cash balances	8,902	(18,240)
Dividends on common stock	(279,962)	(16,605)
Repurchases of common stock	(42,301)	(46,413)
Tax withholding related to net share settlements of restricted stock awards	(1,191)	(679)
Stock options exercised	171	476
Net cash used in financing activities	(89,381)	(31,461)
Effect of exchange rate fluctuations on cash	32	211
Net decrease in cash, cash equivalents and restricted cash	(19,576)	(5,481)
Cash, cash equivalents and restricted cash, beginning of period	33,930	15,131
Cash, cash equivalents and restricted cash, end of period	14,354	9,650
Supplemental disclosures of cash flow information:
Interest paid	4,361	1,699
Income taxes paid	41,038	6,332
Supplemental schedule of non-cash investing and financing activities:
Notes receivable issued upon sale of property and equipment	5,542	8,054
Change in fair value of interest rate swap	(1,651)	377
Property and equipment acquired included in accounts payable	8,847	4,797
Property and equipment disposed included in other receivables	1,486	1,007
Dividends accrued but not yet paid at end of period	$ 6,229	$ 6,407