Derivatives and Risk Management (Fixed Price Swaps Not Designated For Hedge Accounting) (Details) (Year 2014 [Member])	Mar. 31, 2013 ft3
Derivative [Line Items]
Volume of Natural Gas Production (in Bcf), Cash Flow Hedges	18,300,000,000
Not Designated as Hedging Instrument [Member] \| Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of Natural Gas Production (in Bcf), Cash Flow Hedges	181,500,000,000

Volume (in Bcf) of derivative instruments outstanding as of the balance sheet date qualifying as cash flow hedges.

No definition available.

Name:	swn_VolumeOfNaturalGasProductionInBcfCashFlowHedges
Namespace Prefix:	swn_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant