Name:	swn_OtherCommitmentDueAfterEighthYear
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Minimum amount of other commitment maturing in the fifth and eighth fiscal years following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	swn_OtherCommitmentDueInFifthAndEighthYear
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Minimum amount of other commitment maturing in the first through third fiscal years following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	swn_OtherCommitmentDueInFirstThroughThirdYear
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Minimum amount of other commitment maturing in less than twelve months following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	swn_OtherCommitmentDueInLessThanTwelveMonths
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Minimum amount of other commitment maturing in the third through fifth fiscal years following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	swn_OtherCommitmentDueInThirdThroughFifthYear
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	us-gaap_OtherCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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.

Name:	us-gaap_OtherCommitmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Name:	us-gaap_OtherCommitmentsAxis=swn_InfrastructureCurrentlyInServiceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_OtherCommitmentsAxis=swn_PendingRegulatoryApprovalAndOrConstructionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_OtherCommitmentsAxis=swn_FirmTransportationCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: