Condensed Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 60,285	$ 62,524
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	44,772	38,788
(Gain) loss on sale of property and equipment	200	(33)
Other operating activities, net	63,136	71,315
Net cash provided by operating activities	168,393	172,594
Cash flows from investing activities:
Purchase of property and equipment	(120,294)	(72,153)
Proceeds from sale of property and equipment	691	1,851
Net cash used in investing activities	(119,603)	(70,302)
Cash flows from financing activities:
Principal payments under long-term debt agreements	(892)	(10,714)
Proceeds From (Repayments Of) Line Of Credit	(7,591)	0
Payments for share repurchases	(44,646)	(13,327)
Net cash provided by (used in) financing activities	(53,129)	(24,041)
(Decrease) increase in cash and cash equivalents	(4,339)	78,251
Cash and cash equivalents at beginning of period	11,472	34,787
Cash and cash equivalents at end of period	$ 7,133	$ 113,038