Inventory (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Inventory [Abstract]
Current assets inventory, tubulars & other equipment	$ 35.0	$ 34.0
Current assets inventory, underground storage	2.0	4.0
Other assets non-current inventory, gathering systems pipe	$ 17.0	$ 15.0

Carrying amount as of the balance sheet date of tubulars and other equipment used in the E&P segment, and deemed to be a current asset because it is expected to be used within twelve months or in the normal operating cycle.

No definition available.

+ Details

Name:	swn_InventoryTubularsAndOtherEquipment
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of natural gas stored underground in depleted gas reservoirs, aquifers, or salt caverns to meet seasonal and peak load demands, and also as insurance against unforeseen supply disruptions, and deemed to be a current asset because it is expected to be used within twelve months or in the normal operating cycle.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 6

-Subparagraph a

-Article 5

+ Details

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

- Details

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

- Definition

Carrying amount as of the balance sheet date of inventories not expected to be converted to cash, sold or exchanged within the normal operating cycle (such as inventory related to long-term contracts or program rights).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(d))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 6

-Subparagraph d

-Article 5

+ Details

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