Financial Statement Restatement (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Depreciation, depletion and amortization	$ 207,830	$ 171,620	$ 401,457	$ 335,067
Impairment of natural gas and oil properties	800,652		800,652
Deferred income taxes	(253,146)	108,887	(182,596)	197,767
Net loss	(405,132)	167,454	(297,428)	304,063
Loss Per Share:
Basic	$ (1.16)	$ 0.48	$ (0.85)	$ 0.88
Diluted	$ (1.16)	$ 0.48	$ (0.85)	$ 0.87
Cash Flows From Operating Activities
Net loss	(405,132)	167,454	(297,428)	304,063
Impairment of natural gas and oil properties	800,652		800,652
Deferred income taxes	(253,146)	108,887	(182,596)	197,767
CONDENSED CONSOLIDATED BALANCE SHEETS
Accumulated depreciation, depletion and amortization	5,628,635		5,628,635		4,415,339
Deferred income taxes	1,374,259		1,374,259		1,586,798
Retained earnings	2,358,786		2,358,786		2,656,214
Parent [Member]
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Net loss	(405,132)	167,454	(297,428)	304,063
Cash Flows From Operating Activities
Net loss	(405,132)	167,454	(297,428)	304,063
CONDENSED CONSOLIDATED BALANCE SHEETS
Accumulated depreciation, depletion and amortization	67,749		67,749		57,254
Deferred income taxes	(96,715)		(96,715)		(97,045)
Scenario, Previously Reported [Member]
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Impairment of natural gas and oil properties	935,899		935,899
Deferred income taxes	(305,425)		(234,875)
Net loss	(488,100)		(380,396)
Loss Per Share:
Basic	$ (1.40)		$ (1.09)
Diluted	$ (1.40)		$ (1.09)
Cash Flows From Operating Activities
Net loss	(488,100)		(380,396)
Impairment of natural gas and oil properties	935,899		935,899
Deferred income taxes	(305,425)		(234,875)
CONDENSED CONSOLIDATED BALANCE SHEETS
Accumulated depreciation, depletion and amortization	(5,763,882)		(5,763,882)
Deferred income taxes	1,321,980		1,321,980
Retained earnings	2,275,818		2,275,818
As Restated [Member]
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Impairment of natural gas and oil properties	800,652		800,652
Deferred income taxes	(253,146)		(182,596)
Net loss	(405,132)		(297,428)
Loss Per Share:
Basic	$ (1.16)		$ (0.85)
Diluted	$ (1.16)		$ (0.85)
Cash Flows From Operating Activities
Net loss	(405,132)		(297,428)
Impairment of natural gas and oil properties	800,652		800,652
Deferred income taxes	(253,146)		(182,596)
CONDENSED CONSOLIDATED BALANCE SHEETS
Accumulated depreciation, depletion and amortization	(5,628,635)		(5,628,635)
Deferred income taxes	1,374,259		1,374,259
Retained earnings	2,358,786		2,358,786
Scenario, Adjustment [Member]
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Impairment of natural gas and oil properties	82,500
Cash Flows From Operating Activities
Impairment of natural gas and oil properties	$ 82,500