Number of Award Plans Granted

No definition available.

Name:	swn_NumberOfAwardPlansGranted
Namespace Prefix:	swn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation [Line Items]

+ References

No definition available.

+ Details

Name:	swn_ShareBasedCompensationLineItems
Namespace Prefix:	swn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

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

- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

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

- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PlanNameAxis=swn_StockBasedCompensation2013PlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=swn_EquityClassifiedRestrictedStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=swn_LiabilityClassifiedRestrictedStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=swn_LiabilityClassifiedPerformanceUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=swn_RestrictedCashUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-term Incentive Compensation (Narrative) (Details) $ in Millions	6 Months Ended					12 Months Ended	54 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2021 awardType	Jun. 30, 2022 USD ($)
Stock Based Compensation 2013 Plan
Long-term Incentive Compensation [Line Items]
Service period	3 years
Stock options
Long-term Incentive Compensation [Line Items]
Vesting period	3 years
Expiration period	7 years
Restricted stock
Long-term Incentive Compensation [Line Items]
Vesting period	3 years
Equity-classified awards, unrecognized compensation cost	$ 1						$ 1
Weighted average period over which unrecognized cost is recognized, years	1 year 2 months 12 days
Performance units
Long-term Incentive Compensation [Line Items]
Vesting period	3 years						3 years
Equity-classified awards, unrecognized compensation cost	$ 4						$ 4
Weighted average period over which unrecognized cost is recognized, years	2 years 8 months 12 days
Equity-Classified Restricted Stock Units
Long-term Incentive Compensation [Line Items]
Equity-classified awards, unrecognized compensation cost	$ 6						6
Weighted average period over which unrecognized cost is recognized, years	2 years 3 months 18 days
Liability-Classified Restricted Stock Units
Long-term Incentive Compensation [Line Items]
Vesting period	4 years	4 years	4 years	4 years	4 years	3 years
Weighted average period over which unrecognized cost is recognized, years	1 year 3 months 18 days
Liability classified awards, unrecognized compensation costs	$ 16						$ 16
Liability-Classified Performance Units
Long-term Incentive Compensation [Line Items]
Vesting period							3 years
Weighted average period over which unrecognized cost is recognized, years	1 year 9 months 18 days
Liability classified awards, unrecognized compensation costs	$ 14						$ 14
Number of award plans granted \| awardType						2
Performance cash awards
Long-term Incentive Compensation [Line Items]
Vesting period	4 years	4 years
Weighted average period over which unrecognized cost is recognized, years	3 years
Liability classified awards, unrecognized compensation costs	$ 37						$ 37