FAIR VALUE MEASUREMENTS (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reconciliation of changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy
Balance at beginning of period	$ (29,899)	$ 218,942	$ 41,159	$ 195,127
Total Gains or (Losses) (Realized or Unrealized):
Included in Earnings	(272)	69,390	13,056	126,428
Included in Other Comprehensive Income	113,777	(90,234)	42,719	(67,541)
Settlements	272	(68,885)	(13,056)	(125,186)
Transfers In and/or Out of Level 3				385
Balance at end of period	83,878	129,213	83,878	129,213
Natural Gas Revenues
Derivative disclosures
Unrealized gain (loss) included in natural gas revenues	$ 0	$ (342)	$ 0	$ (300)

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

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Amount of gain (loss) recognized in the income statement of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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