Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheets) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Cash and cash equivalents	$ 13,279	$ 16,055	$ 13,948	$ 13,184
Restricted cash	85,002	0
Accounts receivable	336,717	351,573
Inventories	33,378	35,098
Other current assets	217,766	178,167
Total current assets	686,142	580,893
Intercompany receivables	0	0
Investments		0
Property and equipment	9,973,824	8,980,885
Less: Accumulated depreciation, depletion and amortization	4,042,758	3,682,688
Property and equipment, net	5,931,066	5,298,197
Investments in subsidiaries (equity method)	0	0
Other assets	124,893	138,373
TOTAL ASSETS	6,742,101	6,017,463	5,590,351
Accounts and notes payable	594,914	545,095
Other current liabilities	172,435	148,888
Total current liabilities	767,349	693,983
Intercompany payables	0	0
Long-term debt	1,215,400	1,093,000
Deferred income taxes	1,323,970	1,130,292
Other liabilities	128,951	135,312
Total liabilities	3,435,670	3,052,587
Commitments and Contingencies
Total Equity	3,306,431	2,964,876
TOTAL LIABILITIES AND EQUITY	6,742,101	6,017,463
Parent [Member]
Cash and cash equivalents	13,180	8,381	13,834	7,378
Restricted cash	85,002
Accounts receivable	1,485	382
Inventories	43	0
Other current assets	3,875	5,015
Total current assets	103,585	13,778
Intercompany receivables	1,792,206	1,820,857
Investments		0
Property and equipment	158,583	124,823
Less: Accumulated depreciation, depletion and amortization	59,499	52,256
Property and equipment, net	99,084	72,567
Investments in subsidiaries (equity method)	2,589,149	2,253,871
Other assets	26,085	18,918
TOTAL ASSETS	4,610,109	4,179,991
Accounts and notes payable	136,963	175,476
Other current liabilities	3,364	3,288
Total current liabilities	140,327	178,764
Intercompany payables	0	0
Long-term debt	1,215,400	1,093,000
Deferred income taxes	(97,937)	(98,206)
Other liabilities	45,888	41,557
Total liabilities	1,303,678	1,215,115
Commitments and Contingencies
Total Equity	3,306,431	2,964,876
TOTAL LIABILITIES AND EQUITY	4,610,109	4,179,991
Guarantors [Member]
Cash and cash equivalents	0	7,631	22	5,776
Restricted cash	0
Accounts receivable	317,346	331,154
Inventories	32,527	34,263
Other current assets	210,008	171,060
Total current assets	559,881	544,108
Intercompany receivables	50	131
Investments		11,103
Property and equipment	8,738,206	7,871,279
Less: Accumulated depreciation, depletion and amortization	3,870,668	3,526,010
Property and equipment, net	4,867,538	4,345,269
Investments in subsidiaries (equity method)	0	0
Other assets	75,935	92,747
TOTAL ASSETS	5,503,404	4,993,358
Accounts and notes payable	394,049	336,411
Other current liabilities	166,879	142,839
Total current liabilities	560,928	479,250
Intercompany payables	1,315,642	1,317,696
Long-term debt	0	0
Deferred income taxes	1,221,864	1,066,166
Other liabilities	80,409	89,986
Total liabilities	3,178,843	2,953,098
Commitments and Contingencies
Total Equity	2,324,561	2,040,260
TOTAL LIABILITIES AND EQUITY	5,503,404	4,993,358
Non-Guarantors [Member]
Cash and cash equivalents	99	43	92	30
Restricted cash	0
Accounts receivable	17,886	20,037
Inventories	808	835
Other current assets	3,883	2,092
Total current assets	22,676	23,007
Intercompany receivables	20,204	18,724
Investments		(11,102)
Property and equipment	1,077,035	984,783
Less: Accumulated depreciation, depletion and amortization	112,591	104,422
Property and equipment, net	964,444	880,361
Investments in subsidiaries (equity method)	0	0
Other assets	22,873	26,708
TOTAL ASSETS	1,030,197	937,698
Accounts and notes payable	63,902	33,208
Other current liabilities	2,192	2,761
Total current liabilities	66,094	35,969
Intercompany payables	496,818	522,017
Long-term debt	0	0
Deferred income taxes	200,043	162,332
Other liabilities	2,654	3,769
Total liabilities	765,609	724,087
Commitments and Contingencies
Total Equity	264,588	213,611
TOTAL LIABILITIES AND EQUITY	1,030,197	937,698
Eliminations [Member]
Cash and cash equivalents	0	0	0	0
Restricted cash	0
Accounts receivable	0	0
Inventories	0	0
Other current assets	0	0
Total current assets	0	0
Intercompany receivables	(1,812,460)	(1,839,712)
Investments		(1)
Property and equipment	0	0
Less: Accumulated depreciation, depletion and amortization	0	0
Property and equipment, net	0	0
Investments in subsidiaries (equity method)	(2,589,149)	(2,253,871)
Other assets	0	0
TOTAL ASSETS	(4,401,609)	(4,093,584)
Accounts and notes payable	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Intercompany payables	(1,812,460)	(1,839,713)
Long-term debt	0	0
Deferred income taxes	0	0
Other liabilities	0	0
Total liabilities	(1,812,460)	(1,839,713)
Commitments and Contingencies
Total Equity	(2,589,149)	(2,253,871)
TOTAL LIABILITIES AND EQUITY	$ (4,401,609)	$ (4,093,584)