Derivatives - Narrative (Details) BTU in Millions, $ in Millions	6 Months Ended
Jun. 30, 2016 USD ($) BTU
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	$ (24)
Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features	$ 24
Southern Company [Member]
Derivative [Line Items]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints \| BTU	3

Expected volume of natural gas subject to option to sell back excess gas due to operational constraints.

No definition available.

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- Definition

Maximum potential collateral requirements arising the from credit-risk-related contingent features.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

No definition available.

+ Details

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- Definition

The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

+ Details

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