Annual report pursuant to Section 13 and 15(d)

Supplemental Oil and Natural Gas Reserve Data (unaudited) (Summarized Average 12-month Oil and Natural Gas Prices Net of Differentials) (Details)

v2.4.1.9
Supplemental Oil and Natural Gas Reserve Data (unaudited) (Summarized Average 12-month Oil and Natural Gas Prices Net of Differentials) (Details)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Natural Gas [Member]      
Average Sales Price and Production Costs Per Unit of Production [Line Items]      
Average 12-month price, net of differentials 6.38us-gaap_AverageSalesPrices
/ us-gaap_AverageSalesPriceAndProductionCostsPerUnitOfProductionProductionTypeAxis
= us-gaap_NaturalGasReservesMember 		5.45us-gaap_AverageSalesPrices
/ us-gaap_AverageSalesPriceAndProductionCostsPerUnitOfProductionProductionTypeAxis
= us-gaap_NaturalGasReservesMember 		4.81us-gaap_AverageSalesPrices
/ us-gaap_AverageSalesPriceAndProductionCostsPerUnitOfProductionProductionTypeAxis
= us-gaap_NaturalGasReservesMember
Crude Oil [Member]      
Average Sales Price and Production Costs Per Unit of Production [Line Items]      
Average 12-month price, net of differentials 86.30us-gaap_AverageSalesPrices
/ us-gaap_AverageSalesPriceAndProductionCostsPerUnitOfProductionProductionTypeAxis
= us-gaap_CrudeOilMember 		92.16us-gaap_AverageSalesPrices
/ us-gaap_AverageSalesPriceAndProductionCostsPerUnitOfProductionProductionTypeAxis
= us-gaap_CrudeOilMember 		94.68us-gaap_AverageSalesPrices
/ us-gaap_AverageSalesPriceAndProductionCostsPerUnitOfProductionProductionTypeAxis
= us-gaap_CrudeOilMember