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Derivatives And Risk Management (Summary Of Before Tax Effect Of Cash Flow Hedges On Consolidated Financial Statements) (Details) (Fixed Price Swaps [Member], USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income, Effective Portion $ 24us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet $ (90)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
Gas Sales [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative Instruments, Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Earnings, Effective Portion $ 42us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion
/ us-gaap_DerivativeInstrumentRiskAxis
= swn_FixedPriceSwapsMember
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SalesMember		 $ (42)us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion
/ us-gaap_DerivativeInstrumentRiskAxis
= swn_FixedPriceSwapsMember
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SalesMember