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Derivative Instruments (Details Textual) (USD $)
3 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2012
Gas hedges [Member]
Dec. 31, 2011
Gas hedges [Member]
Dec. 31, 2010
Gas hedges [Member]
Dec. 31, 2012
NGL hedges [Member]
Dec. 31, 2011
NGL hedges [Member]
Dec. 31, 2010
NGL hedges [Member]
Dec. 31, 2012
Crude Oil [Member]
Dec. 31, 2011
Crude Oil [Member]
Dec. 31, 2010
Crude Oil [Member]
Derivative Instruments (Textual) [Abstract]                    
Net settlement of hedges   $ 6,846,000 $ 2,609,000 $ 17,538,000 $ 722,000 $ 0 $ 0 $ 1,529,000 $ (192,000) $ 0
Realization of gain, net of taxes 400,000                  
Derivative asset $ 600,000