Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheets) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2009
Cash and cash equivalents	$ 13,293	$ 16,055	$ 14,197	$ 13,184
Restricted cash	69,261	0
Accounts receivable	346,896	351,573
Inventories	46,532	35,098
Other current assets	360,138	178,167
Total current assets	836,120	580,893
Property and equipment	10,444,393	8,980,885
Less: Accumulated depreciation, depletion and amortization	4,230,121	3,682,688
Property and equipment, net	6,214,272	5,298,197
Other assets	163,715	138,373
TOTAL ASSETS	7,214,107	6,017,463	5,992,724
Accounts and notes payable	527,862	545,095
Other current liabilities	238,388	148,888
Total current liabilities	766,250	693,983
Long-term debt	1,271,000	1,093,000
Deferred income taxes	1,461,205	1,130,292
Other liabilities	107,099	135,312
Total liabilities	3,605,554	3,052,587
Commitments and Contingencies
Total Equity	3,608,553	2,964,876
TOTAL LIABILITIES AND EQUITY	7,214,107	6,017,463
Parent [Member]
Cash and cash equivalents	11,842	8,381	12,732	7,378
Restricted cash	69,261
Accounts receivable	273	382
Other current assets	4,557	5,015
Total current assets	85,933	13,778
Intercompany receivables	1,853,309	1,820,857
Property and equipment	175,968	124,823
Less: Accumulated depreciation, depletion and amortization	63,301	52,256
Property and equipment, net	112,667	72,567
Investments in subsidiaries (equity method)	2,902,323	2,253,871
Other assets	23,995	18,918
TOTAL ASSETS	4,978,227	4,179,991
Accounts and notes payable	148,433	175,476
Other current liabilities	3,531	3,288
Total current liabilities	151,964	178,764
Long-term debt	1,271,000	1,093,000
Deferred income taxes	(101,174)	(98,206)
Other liabilities	47,884	41,557
Total liabilities	1,369,674	1,215,115
Commitments and Contingencies
Total Equity	3,608,553	2,964,876
TOTAL LIABILITIES AND EQUITY	4,978,227	4,179,991
Guarantors [Member]
Cash and cash equivalents	1,451	7,631	1,450	5,776
Accounts receivable	322,217	331,154
Inventories	45,629	34,263
Other current assets	352,209	171,060
Total current assets	721,506	544,108
Intercompany receivables	34	131
Investments		11,103
Property and equipment	9,147,370	7,871,279
Less: Accumulated depreciation, depletion and amortization	4,042,935	3,526,010
Property and equipment, net	5,104,435	4,345,269
Other assets	117,782	92,747
TOTAL ASSETS	5,943,757	4,993,358
Accounts and notes payable	334,144	336,411
Other current liabilities	232,632	142,839
Total current liabilities	566,776	479,250
Intercompany payables	1,394,690	1,317,696
Deferred income taxes	1,339,822	1,066,166
Other liabilities	53,234	89,986
Total liabilities	3,354,522	2,953,098
Commitments and Contingencies
Total Equity	2,589,235	2,040,260
TOTAL LIABILITIES AND EQUITY	5,943,757	4,993,358
Non-Guarantors [Member]
Cash and cash equivalents		43	15	30
Accounts receivable	24,406	20,037
Inventories	903	835
Other current assets	3,372	2,092
Total current assets	28,681	23,007
Intercompany receivables	24,961	18,724
Investments		(11,102)
Property and equipment	1,121,055	984,783
Less: Accumulated depreciation, depletion and amortization	123,885	104,422
Property and equipment, net	997,170	880,361
Other assets	21,938	26,708
TOTAL ASSETS	1,072,750	937,698
Accounts and notes payable	45,285	33,208
Other current liabilities	2,225	2,761
Total current liabilities	47,510	35,969
Intercompany payables	483,614	522,017
Deferred income taxes	222,557	162,332
Other liabilities	5,981	3,769
Total liabilities	759,662	724,087
Commitments and Contingencies
Total Equity	313,088	213,611
TOTAL LIABILITIES AND EQUITY	1,072,750	937,698
Eliminations [Member]
Intercompany receivables	(1,878,304)	(1,839,712)
Investments		(1)
Investments in subsidiaries (equity method)	(2,902,323)	(2,253,871)
TOTAL ASSETS	(4,780,627)	(4,093,584)
Intercompany payables	(1,878,304)	(1,839,713)
Total liabilities	(1,878,304)	(1,839,713)
Commitments and Contingencies
Total Equity	(2,902,323)	(2,253,871)
TOTAL LIABILITIES AND EQUITY	$ (4,780,627)	$ (4,093,584)