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Property Acquisitions and Divestitures (Details 2) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Property Acquisitions and Divestitures        
Leasehold acquisition costs $ 224,200,000us-gaap_AcquisitionCosts $ 16,900,000us-gaap_AcquisitionCosts $ 27,800,000us-gaap_AcquisitionCosts $ 17,300,000us-gaap_AcquisitionCosts
Total cumulative leasehold acquisition costs 286,200,000us-gaap_AcquisitionCostsCumulative      
Development costs 15,900,000us-gaap_DevelopmentCosts 2,700,000us-gaap_DevelopmentCosts 2,600,000us-gaap_DevelopmentCosts 1,100,000us-gaap_DevelopmentCosts
Total cumulative development costs 22,300,000us-gaap_DevelopmentCostsCumulative      
Capitalized interest 2,100,000sogc_InterestCapitalizedCosts 5,400,000sogc_InterestCapitalizedCosts 1,300,000sogc_InterestCapitalizedCosts 2,000,000sogc_InterestCapitalizedCosts
Total cumulative capitalized interest 10,800,000sogc_InterestCapitalizedCostsCumulative      
Total unproved oil and natural gas properties 242,200,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization 25,000,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization 31,700,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization 20,400,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortization
Total cumulative unproved oil and natural gas properties $ 319,256,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative $ 208,823,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative    
Leasehold acquisition costs incurred impairment term 10 years