Name:	swn_LiabilityBasedPerformanceUnitsShareBasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition
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Unrecognized cost of unvested liability-based restricted stock share-based compensation awards.

No definition available.

Name:	swn_LiabilityBasedRestrictedStockShareBasedCompensationNonvestedAwardsCompensationCostNotYetRecognized
Namespace Prefix:	swn_
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Weighted average period over which unrecognized compensation is expected to be recognized for liability-based restricted stock compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	swn_LiabilityBasedRestrictedStockShareBasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition
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Data Type:	xbrli:durationItemType
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Period which an employee's right to exercise liability-based performance units are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	swn_ShareBasedCompensationArrangementAwardLiabilityBasedPerformanceUnitsAwardVestingPeriod
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Data Type:	xbrli:durationItemType
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Period which an employee's right to exercise liability-based restricted stock award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	swn_ShareBasedCompensationAwardLiabilityBasedRestrictedStockAwardVestingPeriod
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Data Type:	xbrli:durationItemType
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Period Type:	duration

Share-based Compensation [Line Items]

No definition available.

Name:	swn_ShareBasedCompensationLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

Unrecognized cost of unvested share-based compensation awards.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.