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Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Millions
Dec. 31, 2016
Dec. 31, 2015
Liabilities:    
Weather Derivative Premium $ 4  
Collateral already posted, aggregate fair value 62  
Energy-related derivatives    
Liabilities:    
Collateral already posted, aggregate fair value 8  
Recurring    
Assets:    
Interest rate derivatives 14 $ 22
Nuclear decommissioning trusts:    
Cash equivalents 1,172 790
Other investments 10 10
Fair value assets, total 3,471 2,338
Liabilities:    
Interest rate derivatives 29 30
Contingent consideration 18  
Fair value liabilities, total 735 250
Recurring | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 662 610
Recurring | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 216 207
Recurring | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 92 152
Recurring | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 73 64
Recurring | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 332 289
Recurring | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 183 145
Recurring | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 20 17
Recurring | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 26 25
Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives 671 7
Liabilities:    
Liability Derivatives 630 220
Recurring | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 58  
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Interest rate derivatives 0 0
Nuclear decommissioning trusts:    
Cash equivalents 1,172 790
Other investments 9 9
Fair value assets, total 2,189 1,414
Liabilities:    
Interest rate derivatives 0 0
Contingent consideration 0  
Fair value liabilities, total 345 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 589 541
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 48 47
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 22 11
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 11 16
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives 338 0
Liabilities:    
Liability Derivatives 345 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 0  
Recurring | Significant Other Observable Inputs (Level 2)    
Assets:    
Interest rate derivatives 14 22
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Other investments 0 0
Fair value assets, total 1,261 906
Liabilities:    
Interest rate derivatives 29 30
Contingent consideration 0  
Fair value liabilities, total 372 250
Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 73 69
Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 168 160
Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 92 152
Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 73 64
Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 310 278
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 183 145
Recurring | Significant Other Observable Inputs (Level 2) | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Other Observable Inputs (Level 2) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 15 9
Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives 333 7
Liabilities:    
Liability Derivatives 285 220
Recurring | Significant Other Observable Inputs (Level 2) | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 58  
Recurring | Significant Unobservable Inputs (Level 3)    
Assets:    
Interest rate derivatives 0 0
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Other investments 1 1
Fair value assets, total 1 1
Liabilities:    
Interest rate derivatives 0 0
Contingent consideration 18  
Fair value liabilities, total 18 0
Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Liability Derivatives 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 0  
Alabama Power [Member]    
Assets:    
Energy-related derivatives 20 1
Liabilities:    
Liability Derivatives 9 70
Alabama Power [Member] | Recurring    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts, NAV 20 17
Cash equivalents 262 68
Fair value assets, total 1,072 803
Liabilities:    
Liability Derivatives   70
Alabama Power [Member] | Recurring | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 457 427
Alabama Power [Member] | Recurring | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 95 94
Alabama Power [Member] | Recurring | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 21 27
Alabama Power [Member] | Recurring | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 168 146
Alabama Power [Member] | Recurring | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 19 18
Alabama Power [Member] | Recurring | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 20 17
Nuclear decommissioning trusts, NAV 20 17
Alabama Power [Member] | Recurring | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 10 5
Alabama Power [Member] | Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives 20 1
Liabilities:    
Liability Derivatives 9 55
Alabama Power [Member] | Recurring | Interest rate derivatives    
Liabilities:    
Liability Derivatives   15
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Nuclear decommissioning trusts:    
Cash equivalents 262 68
Fair value assets, total 717 485
Liabilities:    
Liability Derivatives   0
Interest rate derivatives   0
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 385 359
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 48 47
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 22 11
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Liability Derivatives 0  
Alabama Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate derivatives    
Liabilities:    
Liability Derivatives   0
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2)    
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 335 301
Liabilities:    
Liability Derivatives   70
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 72 68
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 47 47
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 21 27
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 146 135
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 19 18
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 10 5
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives 20 1
Liabilities:    
Liability Derivatives 9 55
Alabama Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Interest rate derivatives    
Liabilities:    
Liability Derivatives   15
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3)    
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 0 0
Liabilities:    
Liability Derivatives   0
Interest rate derivatives   0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Liability Derivatives 0  
Alabama Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Interest rate derivatives    
Liabilities:    
Liability Derivatives   0
Georgia Power [Member]    
Assets:    
Energy-related derivatives 46 7
Liabilities:    
Liability Derivatives 11 21
Georgia Power [Member] | Recurring    
Assets:    
Interest rate derivatives   5
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts   63
Cash equivalents   845
Fair value assets, total 860  
Liabilities:    
Liability Derivatives 11 21
Georgia Power [Member] | Recurring | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 205 183
Georgia Power [Member] | Recurring | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 121 113
Georgia Power [Member] | Recurring | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 71 125
Georgia Power [Member] | Recurring | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 73 64
Georgia Power [Member] | Recurring | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 164 143
Georgia Power [Member] | Recurring | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 164 127
Georgia Power [Member] | Recurring | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 16 20
Georgia Power [Member] | Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives 44 2
Liabilities:    
Liability Derivatives 8 15
Georgia Power [Member] | Recurring | Interest rate derivatives    
Assets:    
Interest rate derivatives 2  
Liabilities:    
Liability Derivatives 3 6
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Interest rate derivatives   0
Nuclear decommissioning trusts:    
Cash equivalents 63 261
Fair value assets, total 215  
Liabilities:    
Liability Derivatives 0 0
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 204 182
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 11 16
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Liability Derivatives 0 0
Georgia Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate derivatives    
Assets:    
Interest rate derivatives 0  
Liabilities:    
Liability Derivatives 0 0
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2)    
Assets:    
Interest rate derivatives   5
Nuclear decommissioning trusts:    
Cash equivalents 0 584
Fair value assets, total 645  
Liabilities:    
Liability Derivatives 11 21
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 1 1
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 121 113
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 71 125
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 73 64
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 164 143
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 164 127
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 5 4
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives 44 2
Liabilities:    
Liability Derivatives 8 15
Georgia Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Interest rate derivatives    
Assets:    
Interest rate derivatives 2  
Liabilities:    
Liability Derivatives 3 6
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3)    
Assets:    
Interest rate derivatives   0
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 0  
Liabilities:    
Liability Derivatives 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Domestic equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Foreign equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury and government agency securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Mortgage- and asset-backed securities    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Other    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Liability Derivatives 0 0
Georgia Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Interest rate derivatives    
Assets:    
Interest rate derivatives 0  
Liabilities:    
Liability Derivatives 0 0
Gulf Power [Member]    
Assets:    
Energy-related derivatives 5 1
Liabilities:    
Liability Derivatives 29 100
Gulf Power [Member] | Recurring    
Assets:    
Interest rate derivatives   1
Nuclear decommissioning trusts:    
Cash equivalents 20 18
Fair value assets, total 25 19
Gulf Power [Member] | Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives 5  
Liabilities:    
Liability Derivatives 29 100
Gulf Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Interest rate derivatives   0
Nuclear decommissioning trusts:    
Cash equivalents 20 18
Fair value assets, total 20 18
Gulf Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0  
Liabilities:    
Liability Derivatives 0 0
Gulf Power [Member] | Recurring | Significant Other Observable Inputs (Level 2)    
Assets:    
Interest rate derivatives   1
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 5 1
Gulf Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives 5  
Liabilities:    
Liability Derivatives 29 100
Gulf Power [Member] | Recurring | Significant Unobservable Inputs (Level 3)    
Assets:    
Interest rate derivatives   0
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 0 0
Gulf Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0  
Liabilities:    
Liability Derivatives 0 0
Mississippi Power [Member]    
Assets:    
Energy-related derivatives 7 0
Liabilities:    
Liability Derivatives 11 47
Mississippi Power [Member] | Recurring    
Nuclear decommissioning trusts:    
Cash equivalents 206 52
Fair value assets, total 212  
Mississippi Power [Member] | Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives 3  
Liabilities:    
Liability Derivatives 10 47
Mississippi Power [Member] | Recurring | Interest rate derivatives    
Assets:    
Interest rate derivatives 3  
Mississippi Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Nuclear decommissioning trusts:    
Cash equivalents 206 52
Fair value assets, total 206  
Mississippi Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0  
Liabilities:    
Liability Derivatives 0 0
Mississippi Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate derivatives    
Assets:    
Interest rate derivatives 0  
Mississippi Power [Member] | Recurring | Significant Other Observable Inputs (Level 2)    
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 6  
Mississippi Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives 3  
Liabilities:    
Liability Derivatives 10 47
Mississippi Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Interest rate derivatives    
Assets:    
Interest rate derivatives 3  
Mississippi Power [Member] | Recurring | Significant Unobservable Inputs (Level 3)    
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 0  
Mississippi Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0  
Liabilities:    
Liability Derivatives 0 0
Mississippi Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Interest rate derivatives    
Assets:    
Interest rate derivatives 0  
Southern Power [Member] | Recurring    
Assets:    
Interest rate derivatives 1 3
Nuclear decommissioning trusts:    
Cash equivalents 628 511
Fair value assets, total 650 518
Liabilities:    
Contingent consideration 18  
Fair value liabilities, total 81  
Southern Power [Member] | Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives 21 4
Liabilities:    
Liability Derivatives 5 3
Southern Power [Member] | Recurring | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 58  
Southern Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Interest rate derivatives 0 0
Nuclear decommissioning trusts:    
Cash equivalents 628 511
Fair value assets, total 628 511
Liabilities:    
Contingent consideration 0  
Fair value liabilities, total 0  
Southern Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Liability Derivatives 0 0
Southern Power [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 0  
Southern Power [Member] | Recurring | Significant Other Observable Inputs (Level 2)    
Assets:    
Interest rate derivatives 1 3
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 22 7
Liabilities:    
Contingent consideration 0  
Fair value liabilities, total 63  
Southern Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives 21 4
Liabilities:    
Liability Derivatives 5 3
Southern Power [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 58  
Southern Power [Member] | Recurring | Significant Unobservable Inputs (Level 3)    
Assets:    
Interest rate derivatives 0 0
Nuclear decommissioning trusts:    
Cash equivalents 0 0
Fair value assets, total 0 0
Liabilities:    
Contingent consideration 18  
Fair value liabilities, total 18  
Southern Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0 0
Liabilities:    
Liability Derivatives 0 0
Southern Power [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Foreign currency derivatives    
Liabilities:    
Foreign currency derivatives 0  
Predecessor [Member] | Southern Company Gas [Member]    
Assets:    
Energy-related derivatives   942
Liabilities:    
Liability Derivatives   866
Predecessor [Member] | Southern Company Gas [Member] | Energy-related derivatives    
Liabilities:    
Collateral already posted, aggregate fair value   19
Predecessor [Member] | Southern Company Gas [Member] | Recurring    
Assets:    
Energy-related derivatives   175
Interest rate derivatives   9
Predecessor [Member] | Southern Company Gas [Member] | Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives   166
Liabilities:    
Liability Derivatives   109
Predecessor [Member] | Southern Company Gas [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Energy-related derivatives   53
Interest rate derivatives   0
Predecessor [Member] | Southern Company Gas [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives   53
Liabilities:    
Liability Derivatives   63
Predecessor [Member] | Southern Company Gas [Member] | Recurring | Significant Other Observable Inputs (Level 2)    
Assets:    
Energy-related derivatives   122
Interest rate derivatives   9
Predecessor [Member] | Southern Company Gas [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives   113
Liabilities:    
Liability Derivatives   46
Predecessor [Member] | Southern Company Gas [Member] | Recurring | Significant Unobservable Inputs (Level 3)    
Assets:    
Energy-related derivatives   0
Interest rate derivatives   0
Predecessor [Member] | Southern Company Gas [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives   0
Liabilities:    
Liability Derivatives   0
Successor [Member] | Southern Company Gas [Member]    
Assets:    
Energy-related derivatives 581  
Liabilities:    
Liability Derivatives 569  
Weather Derivative Premium 4 10
Collateral already posted, aggregate fair value 62 96
Successor [Member] | Southern Company Gas [Member] | Energy-related derivatives    
Liabilities:    
Collateral already posted, aggregate fair value 8  
Successor [Member] | Southern Company Gas [Member] | Recurring | Energy-related derivatives    
Assets:    
Energy-related derivatives 577  
Liabilities:    
Liability Derivatives 569  
Successor [Member] | Southern Company Gas [Member] | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy-related derivatives    
Assets:    
Energy-related derivatives 338  
Liabilities:    
Liability Derivatives 345  
Successor [Member] | Southern Company Gas [Member] | Recurring | Significant Other Observable Inputs (Level 2) | Energy-related derivatives    
Assets:    
Energy-related derivatives 239  
Liabilities:    
Liability Derivatives 224  
Successor [Member] | Southern Company Gas [Member] | Recurring | Significant Unobservable Inputs (Level 3) | Energy-related derivatives    
Assets:    
Energy-related derivatives 0  
Liabilities:    
Liability Derivatives 0  
Nuclear Decommissioning Trusts [Member] | Recurring    
Nuclear decommissioning trusts:    
Fair value assets, total 20 17
Nuclear Decommissioning Trusts [Member] | Recurring | Private equity    
Nuclear decommissioning trusts:    
Nuclear decommissioning trusts, NAV $ 20 $ 17