Derivative Instruments (Fair Market Value of Derivative Instruments Included on the Balance Sheet) (Details) (USD $)
9 Months Ended
Sep. 30, 2012
Dec. 31, 2011
Sep. 30, 2012
[MaximumMember]
Dec. 31, 2011
[OilAndGasCommodityDerivativesMember]
[PrepaidExpensesAndOtherCurrentAssetsMember]
Sep. 30, 2012
[OilAndGasCommodityDerivativesMember]
[OtherLiabilitiesMember]
Dec. 31, 2011
[OilAndGasCommodityDerivativesMember]
[OtherLiabilitiesMember]
Derivatives, Fair Value [Line Items]            
Derivative Asset, Fair Value, Net $ 104,000     $ 1,247,000    
Embedded Derivative, Fair Value of Embedded Derivative Liability (14,825,000) (16,067,000)     (14,825,000) (16,067,000)
Derivative, Loss on Derivative     $ 100,000