Condensed Statements Of Cash Flows (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 99,587	$ 53,595
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	66,530	60,500
Loss on sale of property and equipment	900	258
Deferred income taxes	33,679	458
Other operating activities, net	(347)	(4,646)
Net cash provided by operating activities	200,349	110,165
Cash flows from investing activities:
Purchase of property and equipment	(209,900)	(69,148)
Proceeds from sale of property and equipment	5,210	787
Net cash used in investing activities	(204,690)	(68,361)
Cash flows from financing activities:
Proceeds from issuance of long-term debt	96,010	0
Principal payments under long-term debt agreements	(37,027)	(36,548)
Net payments on revolving line of credit	(66,230)	(4,368)
Proceeds from stock issuance, net of issuance costs	48,400	0
Other financing activities, net	0	(2)
Net cash provided by (used in) financing activities	41,153	(40,918)
Increase in cash and cash equivalents	36,812	886
Cash and cash equivalents at beginning of period	5,450	4,171
Cash and cash equivalents at end of period	42,262	5,057
Supplemental disclosure of noncash investing activities:
Acquisition of property and equipment by capital lease	504	722
Fair value of property exchanged	$ 0	$ 1,191