Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsForfeitedInPeriod
Namespace Prefix:	swn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Share-Based Compensation Arrangement By Share-Based Payment Award, Liability Instruments Other Than Options, Forfeitures In Period, Weighted Average Fair Value

No definition available.

Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsForfeituresInPeriodWeightedAverageFairValue
Namespace Prefix:	swn_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The number of liability grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

No definition available.

Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	swn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Share-Based Compensation Arrangement By Share-Based Payment Award, Liability Instruments Other Than Options, Grants In Period, Weighted Average Fair Value

No definition available.

Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageFairValue
Namespace Prefix:	swn_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The number of non-vested liability-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

No definition available.

Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix:	swn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Share-based Compensation Arrangement by Share-based Payment Award, Liability Instruments Other than Options, Nonvested, Weighted Average Fair Value

No definition available.

Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsNonvestedWeightedAverageFairValue
Namespace Prefix:	swn_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

The number of liability-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

No definition available.

Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix:	swn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Share-Based Compensation Arrangement By Share-Based Payment Award, Liability Instruments Other Than Options, Vested In Period, Weighted Average Fair Value

No definition available.

Name:	swn_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageFairValue
Namespace Prefix:	swn_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.