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Fair Value Measurements (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Increase Decrease in Fair Value of Funds Including Reinvested Interest and Dividends $ 53 $ 116
Fair Value, Measurements, Recurring [Member]
    
Assets:    
Energy-related derivatives 48 48
Interest rate derivatives 13 13
Nuclear decommissioning trusts 1,280 [1] 1,280 [1]
Cash equivalents 909 909
Other 24 24
Fair value assets, total 2,274 2,274
Liabilities:    
Energy-related derivatives 111 111
Interest rate derivatives 32 32
Fair value liabilities, total 143 143
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
    
Assets:    
Energy-related derivatives 0 0
Interest rate derivatives 0 0
Nuclear decommissioning trusts 476 [1] 476 [1]
Cash equivalents 909 909
Other 9 9
Fair value assets, total 1,394 1,394
Liabilities:    
Energy-related derivatives 0 0
Interest rate derivatives 0 0
Fair value liabilities, total 0 0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
    
Assets:    
Energy-related derivatives 48 48
Interest rate derivatives 13 13
Nuclear decommissioning trusts 804 [1] 804 [1]
Cash equivalents 0 0
Other 0 0
Fair value assets, total 865 865
Liabilities:    
Energy-related derivatives 111 111
Interest rate derivatives 32 32
Fair value liabilities, total 143 143
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
    
Assets:    
Energy-related derivatives 0 0
Interest rate derivatives 0 0
Nuclear decommissioning trusts 0 [1] 0 [1]
Cash equivalents 0 0
Other 15 15
Fair value assets, total 15 15
Liabilities:    
Energy-related derivatives 0 0
Interest rate derivatives 0 0
Fair value liabilities, total 0 0
Alabama Power [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Increase Decrease in Fair Value of Funds Including Reinvested Interest and Dividends 27 60
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member]
    
Assets:    
Energy-related derivatives 11 11
Fair value assets, total 842 842
Liabilities:    
Energy-related derivatives 19 19
Interest rate derivatives 32 32
Fair value liabilities, total 51 51
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 352 [2] 352 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 79 [2],[3] 79 [2],[3]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 27 [2] 27 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 103 [2] 103 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 26 [2] 26 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 9 [2] 9 [2]
Cash equivalents 235 235
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
    
Assets:    
Energy-related derivatives 0 0
Fair value assets, total 551 551
Liabilities:    
Energy-related derivatives 0 0
Interest rate derivatives 0 0
Fair value liabilities, total 0 0
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 289 [2] 289 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 27 [2],[3] 27 [2],[3]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
    
Assets:    
Energy-related derivatives 11 11
Fair value assets, total 291 291
Liabilities:    
Energy-related derivatives 19 19
Interest rate derivatives 32 32
Fair value liabilities, total 51 51
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 63 [2] 63 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 52 [2],[3] 52 [2],[3]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 27 [2] 27 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 103 [2] 103 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 26 [2] 26 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 9 [2] 9 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
    
Assets:    
Energy-related derivatives 0 0
Fair value assets, total 0 0
Liabilities:    
Energy-related derivatives 0 0
Interest rate derivatives 0 0
Fair value liabilities, total 0 0
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Alabama Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2] 0 [2]
Cash equivalents 0 0
Georgia Power [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Increase Decrease in Fair Value of Funds Including Reinvested Interest and Dividends 26 56
Assets:    
Nuclear decommissioning trusts 54 54
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member]
    
Assets:    
Energy-related derivatives 19 19
Cash equivalents 288 288
Fair value assets, total 991 991
Liabilities:    
Energy-related derivatives 46 46
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 161 [2],[3] 161 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 110 [2],[3],[4] 110 [2],[3],[4]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 69 [2],[3] 69 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Municipal bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 93 [2],[3] 93 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 128 [2],[3] 128 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 110 [2],[3] 110 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 13 [2],[3] 13 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
    
Assets:    
Energy-related derivatives 0 0
Cash equivalents 288 288
Fair value assets, total 448 448
Liabilities:    
Energy-related derivatives 0 0
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 160 [2],[3] 160 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3],[4] 0 [2],[3],[4]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Municipal bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
    
Assets:    
Energy-related derivatives 19 19
Cash equivalents 0 0
Fair value assets, total 543 543
Liabilities:    
Energy-related derivatives 46 46
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 1 [2],[3] 1 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 110 [2],[3],[4] 110 [2],[3],[4]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 69 [2],[3] 69 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Municipal bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 93 [2],[3] 93 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 128 [2],[3] 128 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 110 [2],[3] 110 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 13 [2],[3] 13 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
    
Assets:    
Energy-related derivatives 0 0
Cash equivalents 0 0
Fair value assets, total 0 0
Liabilities:    
Energy-related derivatives 0 0
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign Equity [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3],[4] 0 [2],[3],[4]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury and government agency securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Municipal bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate bonds [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mortgage and asset backed securities [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Georgia Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other investments [Member]
    
Assets:    
Nuclear decommissioning trusts 0 [2],[3] 0 [2],[3]
Gulf Power [Member] | Fair Value, Measurements, Recurring [Member]
    
Assets:    
Energy-related derivatives 11 11
Cash equivalents 15 15
Fair value assets, total 26 26
Liabilities:    
Energy-related derivatives 24 24
Gulf Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
    
Assets:    
Energy-related derivatives 0 0
Cash equivalents 15 15
Fair value assets, total 15 15
Liabilities:    
Energy-related derivatives 0 0
Gulf Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
    
Assets:    
Energy-related derivatives 11 11
Cash equivalents 0 0
Fair value assets, total 11 11
Liabilities:    
Energy-related derivatives 24 24
Gulf Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
    
Assets:    
Energy-related derivatives 0 0
Cash equivalents 0 0
Fair value assets, total 0 0
Liabilities:    
Energy-related derivatives 0 0
Mississippi Power [Member] | Fair Value, Measurements, Recurring [Member]
    
Assets:    
Energy-related derivatives 5 5
Cash equivalents 192 192
Fair value assets, total 197 197
Liabilities:    
Energy-related derivatives 20 20
Mississippi Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
    
Assets:    
Energy-related derivatives 0 0
Cash equivalents 192 192
Fair value assets, total 192 192
Liabilities:    
Energy-related derivatives 0 0
Mississippi Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
    
Assets:    
Energy-related derivatives 5 5
Cash equivalents 0 0
Fair value assets, total 5 5
Liabilities:    
Energy-related derivatives 20 20
Mississippi Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
    
Assets:    
Energy-related derivatives 0 0
Cash equivalents 0 0
Fair value assets, total 0 0
Liabilities:    
Energy-related derivatives 0 0
Southern Power [Member] | Fair Value, Measurements, Recurring [Member]
    
Assets:    
Energy-related derivatives 2 2
Liabilities:    
Energy-related derivatives 2 2
Southern Power [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Energy-related derivatives 0 0
Southern Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
    
Assets:    
Energy-related derivatives 2 2
Liabilities:    
Energy-related derivatives 2 2
Southern Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Energy-related derivatives $ 0 $ 0
[1] For additional detail, see the nuclear decommissioning trusts sections for Alabama Power and Georgia Power in this table.
[2] Excludes receivables related to investment income, pending investment sales, and payables related to pending investment purchases.
[3] Includes the investment securities pledged to creditors and cash collateral received and payables related to the securities lending program. As of September 30, 2012, approximately $54 million of the fair market value of Georgia Power's nuclear decommissioning trust funds' securities were on loan and pledged to creditors under the funds' managers' securities lending program.
[4] Level 1 securities consist of actively traded stocks, while Level 2 securities consist of pooled funds.