Fair Value Measurements (Details 3) (USD $) In Millions	Sep. 30, 2011
Long-term debt:
Long-term debt, Carrying Amount	$ 20,532
Long-term debt, Fair Value	22,215
Alabama Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	6,232
Long-term debt, Fair Value	6,910
Georgia Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	8,620
Long-term debt, Fair Value	9,327
Gulf Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,235
Long-term debt, Fair Value	1,359
Mississippi Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	702
Long-term debt, Fair Value	739
Southern Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,599
Long-term debt, Fair Value	$ 1,694

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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 210.5-02.22)

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

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number APB14-1

-Paragraph 31

-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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant