DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Effect of derivative instruments on the Condensed Consolidated Statement of Operations
Ineffectiveness related to derivative instruments	$ 0	$ 0	$ 0	$ 0
Natural Gas Revenues
Effect of derivative instruments on the Condensed Consolidated Statement of Operations
Amount of Gain (Loss) Recognized in Income on Derivatives Not Designated	0	(149)	0	(449)
Derivatives Designated as Hedging Instruments
Effect of derivative instruments on the Condensed Consolidated Statement of Operations
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	19,684	60,938	36,876	189,450
Derivatives Designated as Hedging Instruments | Natural Gas Revenues
Effect of derivative instruments on the Condensed Consolidated Statement of Operations
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	20,766	57,139	33,822	183,867
Derivatives Designated as Hedging Instruments | Crude Oil and Condensate Revenues
Effect of derivative instruments on the Condensed Consolidated Statement of Operations
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1,082)	3,799	3,054	5,583
Derivatives Designated as Hedging Instruments | Commodity contracts
Effect of derivative instruments on the Condensed Consolidated Statement of Operations
Amount of Gain (Loss) Recognized In OCI on Derivatives (Effective Portion)	$ (2,384)	$ (39,805)	$ 51,783	$ 49,299