Condensed Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 133,323	$ 109,333
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	63,073	53,481
Loss on sale of property and equipment	477	364
Share-based compensation	1,933	1,132
Other operating activities, net	7,369	46,937
Net cash provided by operating activities	206,175	211,247
Cash flows from investing activities:
Purchase of property and equipment	(70,741)	(100,558)
Proceeds from sale of property and equipment	277	347
Net cash used in investing activities	(70,464)	(100,211)
Cash flows from financing activities:
Principal payments under long-term debt agreements		(50,000)
Payments for share repurchases	(30,596)	(17,299)
Dividends paid	(13,790)	(10,695)
Other financing activities, net	(980)	(567)
Net cash used in financing activities	(45,366)	(78,561)
Increase in cash and cash equivalents	90,345	32,475
Cash and cash equivalents at beginning of period	190,282	127,462
Cash and cash equivalents at end of period	$ 280,627	$ 159,937