Derivative Financial Instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Natural Gas Commodity Derivatives [Abstract]
Realized (loss) gain on commodity derivatives	$ 62,537,000	$ 45,040,000
Unrealized Gain (Loss) on Derivatives	57,746,000	(29,405,000)
Gain loss on commodity derivatives	120,283,000	15,635,000
Swap [Member] | Nymex [Member] | Calendar 2012 [Member]
Schedule Of Derivative Instruments [Line Items]
Derivative, Underlying Basis	500,000
Derivative, Swap Type, Average Fixed Price	4.23
Derivative Asset, Fair Value	237,201,000
Swap [Member] | Nymex [Member] | Summer 2012 [Member]
Schedule Of Derivative Instruments [Line Items]
Derivative, Underlying Basis	90,000
Derivative, Swap Type, Average Fixed Price	5.00
Derivative Asset, Fair Value	$ 50,931,000