Organization And Summary Of Significant Accounting Policies (Schedule Of Supplemental Disclosures Of Cash Flow Information) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization And Summary Of Significant Accounting Policies [Abstract]
Cash paid during the year for interest, net of amounts capitalized	$ 6	$ 50	$ 36
Cash paid (received) during the year for income taxes	(6)	28	19
Increase (decrease) in noncash property additions	$ (10)	$ 174	$ (13)

Increase in noncash property additions as relates to supplemental disclosures of cash flow information.

No definition available.

Name:	swn_IncreaseDecreaseInNoncashPropertyAdditions
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586

+ Details

Name:	us-gaap_IncomeTaxesPaidNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of cash paid for interest during the period net of cash paid for interest that is capitalized.

+ References

+ Details

Name:	us-gaap_InterestPaidNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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