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Derivative Instruments and Hedging Activities - Impact of Rights of Offset Associated with Recognized Assets and Liabilities (Detail) (USD $)
In Thousands, unless otherwise specified
0 Months Ended 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Derivative Instruments And Hedging Activities [Line Items]    
Fair Value of Derivative Instruments, Assets Effect of Netting $ 0sgy_DerivativeAssetFairValueNettingAdjustment  
Current Asset [Member]    
Derivative Instruments And Hedging Activities [Line Items]    
Fair Value of Derivative Instruments, Assets With Effects of Netting   4,549sgy_DerivativeAssetsLiabilitiesFairValueGrossAssetNet
/ us-gaap_BalanceSheetLocationAxis
= sgy_CurrentAssetMember
Fair Value of Derivative Instruments, Assets Effect of Netting   (4,043)sgy_DerivativeAssetFairValueNettingAdjustment
/ us-gaap_BalanceSheetLocationAxis
= sgy_CurrentAssetMember
Fair Value of Derivative Instruments, Assets Without Netting   506us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement
/ us-gaap_BalanceSheetLocationAxis
= sgy_CurrentAssetMember
Long-term assets [Member]    
Derivative Instruments And Hedging Activities [Line Items]    
Fair Value of Derivative Instruments, Assets With Effects of Netting   1,378sgy_DerivativeAssetsLiabilitiesFairValueGrossAssetNet
/ us-gaap_BalanceSheetLocationAxis
= sgy_LongTermAssetsMember
Fair Value of Derivative Instruments, Assets Effect of Netting   (274)sgy_DerivativeAssetFairValueNettingAdjustment
/ us-gaap_BalanceSheetLocationAxis
= sgy_LongTermAssetsMember
Fair Value of Derivative Instruments, Assets Without Netting   1,104us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement
/ us-gaap_BalanceSheetLocationAxis
= sgy_LongTermAssetsMember
Current liabilities [Member]    
Derivative Instruments And Hedging Activities [Line Items]    
Fair Value of Derivative Instruments, Liabilities With Effects of Netting   (7,753)sgy_DerivativeAssetsLiabilitiesFairValueGrossLiabilityNet
/ us-gaap_BalanceSheetLocationAxis
= sgy_CurrentLiabilitiesMember
Fair Value of Derivative Instruments, Liabilities Effect of Netting   4,043sgy_DerivativeLiabilityFairValueNettingAdjustment
/ us-gaap_BalanceSheetLocationAxis
= sgy_CurrentLiabilitiesMember
Fair Value of Derivative Instruments, Liabilities Without Netting   (3,710)us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement
/ us-gaap_BalanceSheetLocationAxis
= sgy_CurrentLiabilitiesMember
Long-term liabilities [Member]    
Derivative Instruments And Hedging Activities [Line Items]    
Fair Value of Derivative Instruments, Liabilities With Effects of Netting   (470)sgy_DerivativeAssetsLiabilitiesFairValueGrossLiabilityNet
/ us-gaap_BalanceSheetLocationAxis
= sgy_LongTermLiabilitiesMember
Fair Value of Derivative Instruments, Liabilities Effect of Netting   274sgy_DerivativeLiabilityFairValueNettingAdjustment
/ us-gaap_BalanceSheetLocationAxis
= sgy_LongTermLiabilitiesMember
Fair Value of Derivative Instruments, Liabilities Without Netting   $ (196)us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement
/ us-gaap_BalanceSheetLocationAxis
= sgy_LongTermLiabilitiesMember