Fair Value Measurements (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
Fair Value Measurements (Textual) [Abstract]
Increase in fair value of funds including reinvested interest and dividends	$ 86
Fair Value Measurement (Textual) [Abstract]
Maximum number of months related to maturities in the portfolio not to exceeded from date of purchase	13 months
Maximum number of days related to dollar-weighted average portfolio maturities regarding commingled funds	90 days
Maximum maturity for longer term investment grade fixed income obligations (in years)	5 years
Minimum number of months related to the reset date of maturities in the portfolio with put features or floating rates	13 months
Alabama Power [Member]
Fair Value Measurements (Textual) [Abstract]
Increase in fair value of funds including reinvested interest and dividends	49
Georgia Power [Member]
Fair Value Measurements (Textual) [Abstract]
Nuclear decommissioning trusts	41
Increase in fair value of funds including reinvested interest and dividends	$ 37

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- Definition

Increase (decrease) in fair value of funds including reinvested interest and dividends.

+ References

No definition available.

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- Definition

Maximum maturity for longer term investment grade fixed income obligations.

+ References

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- Definition

Maximum number of days related to dollar weighted average portfolio maturities regarding commingled funds.

+ References

No definition available.

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- Definition

Maximum number of months related to maturities in the portfolio not to exceeded from date of purchase.

+ References

No definition available.

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- Definition

Minimum number of months related to the reset date of maturities in the portfolio with put features or floating rates.

+ References

No definition available.

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- Definition

The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 143

-Paragraph 22

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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