Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 36,086	$ 27,807
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	60,759	55,506
Deferred income taxes	425	5,478
Gain on disposal of property and equipment	(5,929)	(2,708)
Non-cash equity compensation	2,051	1,410
Insurance and claims accruals, net of current portion	5,940	290
Other	(2,748)	(1,779)
Changes in certain working capital items:
Accounts receivable, net	24,403	2,207
Other current assets	6,216	5,320
Accounts payable	3,642	3,822
Other current liabilities	7,924	2,509
Net cash provided by operating activities	138,769	99,862
Cash flows from investing activities:
Additions to property and equipment	(120,357)	(94,237)
Proceeds from sales of property and equipment	36,993	38,731
Decrease in notes receivable	3,426	5,944
Net cash used in investing activities	(79,938)	(49,562)
Cash flows from financing activities:
Change in net checks issued in excess of cash balances	0	(21,539)
Dividends on common stock	(6,340)	(5,068)
Repurchases of common stock	(20,545)	0
Tax withholding related to net share settlements of restricted stock awards	(1,179)	(667)
Stock options exercised	0	229
Net cash used in financing activities	(28,064)	(27,045)
Effect of exchange rate fluctuations on cash	45	403
Net increase in cash, cash equivalents and restricted cash	30,812	23,658
Cash, cash equivalents and restricted cash, beginning of period	33,930	15,131
Cash, cash equivalents and restricted cash, end of period	64,742	38,789
Supplemental disclosures of cash flow information:
Interest paid	864	481
Income taxes paid	556	301
Supplemental schedule of non-cash investing and financing activities:
Notes receivable issued upon sale of property and equipment	2,092	2,178
Change in fair value of interest rate swap	(105)	278
Property and equipment acquired included in accounts payable	15,050	5,999
Property and equipment disposed included in other receivables	72	67
Dividends accrued but not yet paid at end of period	$ 6,290	$ 5,071