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Discontinued Operations Narrative (Details) (USD $)
3 Months Ended 9 Months Ended 1 Months Ended 3 Months Ended
Mar. 31, 2012
Sep. 30, 2013
Sep. 30, 2012
Dec. 31, 2012
Black Warrior Basin Properties
Natural Gas
Mcf
Oct. 31, 2013
Black Warrior Basin Properties
Alabama
Subsequent Event
Sep. 30, 2013
North Louisiana and East Texas Natural Gas and Oil Properties
Dec. 31, 2012
North Louisiana and East Texas Natural Gas and Oil Properties
Natural Gas
Mcf
Dec. 31, 2012
North Louisiana and East Texas Natural Gas and Oil Properties
Oil
bbl
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                
Proceeds from the sale of oil and gas property         $ 160,000,000      
Gain on disposition of oil and gas property         35,000,000      
Proved Developed Reserves (Volume)       97,000,000     20,000,000 0
Impairment of oil and gas properties held-for-sale           24,600,000    
Asset impairment $ 21,500,000 $ 24,612,000 $ 21,545,000          
Discount rate   10.00%