Quarterly report pursuant to Section 13 or 15(d)

Asset Retirement Obligations (Details)

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Asset Retirement Obligations (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Asset Retirement Obligations    
Asset retirement obligations - beginning of period $ 16,614us-gaap_AssetRetirementObligationsNoncurrent  
Obligations incurred for wells drilled 1,309us-gaap_AssetRetirementObligationLiabilitiesIncurred  
Accretion expense 400us-gaap_AssetRetirementObligationAccretionExpense 302us-gaap_AssetRetirementObligationAccretionExpense
Asset retirement obligations - end of period $ 18,323us-gaap_AssetRetirementObligationsNoncurrent