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RETIREMENT BENEFITS - Fair Values of Pension Plan and Other Postretirement Benefit Plan Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2023
Dec. 31, 2022
Assets:    
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Pension plans    
Assets:    
Plan assets $ 14,760 $ 14,197
Target Allocation   100.00%
Actual Allocation   100.00%
Derivatives   $ (4)
Total   $ 14,193
Pension plans | Equity    
Assets:    
Target Allocation 41.00% 45.00%
Actual Allocation 40.00% 43.00%
Pension plans | Domestic equity    
Assets:    
Plan assets $ 2,730 $ 2,769
Pension plans | International equity    
Assets:    
Plan assets $ 2,999 $ 3,256
Pension plans | Fixed income    
Assets:    
Target Allocation 30.00% 30.00%
Actual Allocation 32.00% 28.00%
Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 1,973 $ 1,469
Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 44 29
Pension plans | Corporate bonds    
Assets:    
Plan assets 1,724 1,494
Pension plans | Pooled funds    
Assets:    
Plan assets 777 607
Pension plans | Cash equivalents and other    
Assets:    
Plan assets 429 406
Pension plans | Real estate investments    
Assets:    
Plan assets $ 2,053 $ 2,263
Target Allocation 12.00% 13.00%
Actual Allocation 14.00% 15.00%
Pension plans | Special situations    
Assets:    
Plan assets $ 245 $ 187
Target Allocation 3.00% 3.00%
Actual Allocation 2.00% 2.00%
Pension plans | Private equity    
Assets:    
Plan assets $ 1,761 $ 1,717
Target Allocation 9.00% 9.00%
Actual Allocation 12.00% 12.00%
Pension plans | Private Credit    
Assets:    
Plan assets $ 25  
Target Allocation 3.00%  
Actual Allocation 0.00%  
Pension plans | Infrastructure    
Assets:    
Plan assets $ 0  
Target Allocation 2.00%  
Actual Allocation 0.00%  
Other postretirement benefit plans    
Assets:    
Plan assets $ 1,096 $ 998
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Other postretirement benefit plans | Equity    
Assets:    
Target Allocation 60.00% 61.00%
Actual Allocation 61.00% 59.00%
Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets $ 172 $ 159
Other postretirement benefit plans | International equity    
Assets:    
Plan assets $ 135 $ 137
Other postretirement benefit plans | Fixed income    
Assets:    
Target Allocation 30.00% 30.00%
Actual Allocation 28.00% 28.00%
Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 57 $ 43
Other postretirement benefit plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 2 1
Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 47 40
Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 92 79
Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 23 19
Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 456 406
Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets $ 57 $ 62
Target Allocation 4.00% 5.00%
Actual Allocation 6.00% 7.00%
Other postretirement benefit plans | Special situations    
Assets:    
Plan assets $ 6 $ 6
Target Allocation 1.00% 1.00%
Actual Allocation 1.00% 1.00%
Other postretirement benefit plans | Private equity    
Assets:    
Plan assets $ 48 $ 46
Target Allocation 3.00% 3.00%
Actual Allocation 4.00% 5.00%
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans    
Assets:    
Plan assets $ 4,646 $ 5,019
Derivatives   (4)
Total   5,015
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Domestic equity    
Assets:    
Plan assets 1,959 2,078
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | International equity    
Assets:    
Plan assets 1,947 2,166
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 371 399
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Real estate investments    
Assets:    
Plan assets 369 376
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans    
Assets:    
Plan assets 170 173
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 85 85
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 53 58
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 21 19
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 11 11
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Significant Other Observable Inputs (Level 2) | Pension plans    
Assets:    
Plan assets 6,399 5,387
Derivatives   0
Total   5,387
Significant Other Observable Inputs (Level 2) | Pension plans | Domestic equity    
Assets:    
Plan assets 771 691
Significant Other Observable Inputs (Level 2) | Pension plans | International equity    
Assets:    
Plan assets 1,052 1,090
Significant Other Observable Inputs (Level 2) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 1,973 1,469
Significant Other Observable Inputs (Level 2) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 44 29
Significant Other Observable Inputs (Level 2) | Pension plans | Corporate bonds    
Assets:    
Plan assets 1,724 1,494
Significant Other Observable Inputs (Level 2) | Pension plans | Pooled funds    
Assets:    
Plan assets 777 607
Significant Other Observable Inputs (Level 2) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 58 7
Significant Other Observable Inputs (Level 2) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Significant Other Observable Inputs (Level 2) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Significant Other Observable Inputs (Level 2) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Significant Other Observable Inputs (Level 2) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Significant Other Observable Inputs (Level 2) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans    
Assets:    
Plan assets 825 722
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 87 74
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 82 79
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 57 43
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 2 1
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 47 40
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 92 79
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 2 0
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 456 406
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 0 0
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans    
Assets:    
Plan assets 0 0
Derivatives   0
Significant Unobservable Inputs (Level 3) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Significant Unobservable Inputs (Level 3) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Significant Unobservable Inputs (Level 3) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Net Asset Value as a Practical Expedient (NAV) | Pension plans    
Assets:    
Plan assets 3,715 3,791
Derivatives   0
Total   3,791
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Real estate investments    
Assets:    
Plan assets 1,684 1,887
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Special situations    
Assets:    
Plan assets 245 187
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private equity    
Assets:    
Plan assets 1,761 1,717
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private Credit    
Assets:    
Plan assets 25  
Net Asset Value as a Practical Expedient (NAV) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans    
Assets:    
Plan assets 101 103
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 0 0
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 46 51
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 6 6
Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 48 $ 46
Alabama Power    
Assets:    
Target Allocation   100.00%
Actual Allocation   100.00%
Alabama Power | Pension plans    
Assets:    
Plan assets $ 3,579 $ 3,422
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Derivatives   $ (1)
Total   $ 3,421
Alabama Power | Pension plans | Equity    
Assets:    
Target Allocation 41.00% 45.00%
Actual Allocation 40.00% 43.00%
Alabama Power | Pension plans | Domestic equity    
Assets:    
Plan assets $ 663 $ 667
Alabama Power | Pension plans | International equity    
Assets:    
Plan assets $ 727 $ 785
Alabama Power | Pension plans | Fixed income    
Assets:    
Target Allocation 30.00% 30.00%
Actual Allocation 32.00% 28.00%
Alabama Power | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 479 $ 354
Alabama Power | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 11 7
Alabama Power | Pension plans | Corporate bonds    
Assets:    
Plan assets 418 360
Alabama Power | Pension plans | Pooled funds    
Assets:    
Plan assets 188 146
Alabama Power | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 104 98
Alabama Power | Pension plans | Real estate investments    
Assets:    
Plan assets $ 497 $ 546
Target Allocation 12.00% 13.00%
Actual Allocation 14.00% 15.00%
Alabama Power | Pension plans | Special situations    
Assets:    
Plan assets $ 59 $ 45
Target Allocation 3.00% 3.00%
Actual Allocation 2.00% 2.00%
Alabama Power | Pension plans | Private equity    
Assets:    
Plan assets $ 427 $ 414
Target Allocation 9.00% 9.00%
Actual Allocation 12.00% 12.00%
Alabama Power | Pension plans | Private Credit    
Assets:    
Plan assets $ 6  
Target Allocation 3.00%  
Actual Allocation 0.00%  
Alabama Power | Pension plans | Infrastructure    
Assets:    
Plan assets $ 0  
Target Allocation 2.00%  
Actual Allocation 0.00%  
Alabama Power | Other postretirement benefit plans    
Assets:    
Plan assets $ 402 $ 371
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Alabama Power | Other postretirement benefit plans | Equity    
Assets:    
Target Allocation 67.00% 69.00%
Actual Allocation 66.00% 65.00%
Alabama Power | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets $ 22 $ 23
Alabama Power | Other postretirement benefit plans | International equity    
Assets:    
Plan assets $ 25 $ 27
Alabama Power | Other postretirement benefit plans | Fixed income    
Assets:    
Target Allocation 23.00% 23.00%
Actual Allocation 23.00% 23.00%
Alabama Power | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 16 $ 12
Alabama Power | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 14 12
Alabama Power | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 8 7
Alabama Power | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 3 3
Alabama Power | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 280 252
Alabama Power | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets $ 17 $ 19
Target Allocation 4.00% 4.00%
Actual Allocation 6.00% 7.00%
Alabama Power | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets $ 2 $ 2
Target Allocation 1.00% 1.00%
Actual Allocation 1.00% 1.00%
Alabama Power | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets $ 15 $ 14
Target Allocation 3.00% 3.00%
Actual Allocation 4.00% 4.00%
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans    
Assets:    
Plan assets $ 1,127 $ 1,209
Derivatives   (1)
Total   1,208
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Domestic equity    
Assets:    
Plan assets 476 500
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | International equity    
Assets:    
Plan assets 472 522
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 90 96
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Real estate investments    
Assets:    
Plan assets 89 91
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans    
Assets:    
Plan assets 38 41
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 16 17
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 16 18
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 3 3
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 3 3
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Alabama Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans    
Assets:    
Plan assets 1,552 1,299
Derivatives   0
Total   1,299
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Domestic equity    
Assets:    
Plan assets 187 167
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | International equity    
Assets:    
Plan assets 255 263
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 479 354
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 11 7
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Corporate bonds    
Assets:    
Plan assets 418 360
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Pooled funds    
Assets:    
Plan assets 188 146
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 14 2
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Alabama Power | Significant Other Observable Inputs (Level 2) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans    
Assets:    
Plan assets 333 298
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 6 6
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 9 9
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 16 12
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 14 12
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 8 7
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 280 252
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 0 0
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Alabama Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans    
Assets:    
Plan assets 0 0
Derivatives   0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Alabama Power | Significant Unobservable Inputs (Level 3) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans    
Assets:    
Plan assets 900 914
Derivatives   0
Total   914
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Real estate investments    
Assets:    
Plan assets 408 455
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Special situations    
Assets:    
Plan assets 59 45
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private equity    
Assets:    
Plan assets 427 414
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private Credit    
Assets:    
Plan assets 6  
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans    
Assets:    
Plan assets 31 32
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 0 0
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 14 16
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 2 2
Alabama Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 15 $ 14
Georgia Power    
Assets:    
Target Allocation   100.00%
Actual Allocation   100.00%
Georgia Power | Pension plans    
Assets:    
Plan assets $ 4,615 $ 4,448
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Derivatives   $ (1)
Total   $ 4,447
Georgia Power | Pension plans | Equity    
Assets:    
Target Allocation 41.00% 45.00%
Actual Allocation 40.00% 43.00%
Georgia Power | Pension plans | Domestic equity    
Assets:    
Plan assets $ 852 $ 868
Georgia Power | Pension plans | International equity    
Assets:    
Plan assets $ 938 $ 1,020
Georgia Power | Pension plans | Fixed income    
Assets:    
Target Allocation 30.00% 30.00%
Actual Allocation 32.00% 28.00%
Georgia Power | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 617 $ 460
Georgia Power | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 14 9
Georgia Power | Pension plans | Corporate bonds    
Assets:    
Plan assets 539 468
Georgia Power | Pension plans | Pooled funds    
Assets:    
Plan assets 243 190
Georgia Power | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 134 127
Georgia Power | Pension plans | Real estate investments    
Assets:    
Plan assets $ 642 $ 709
Target Allocation 12.00% 13.00%
Actual Allocation 14.00% 15.00%
Georgia Power | Pension plans | Special situations    
Assets:    
Plan assets $ 77 $ 59
Target Allocation 3.00% 3.00%
Actual Allocation 2.00% 2.00%
Georgia Power | Pension plans | Private equity    
Assets:    
Plan assets $ 551 $ 538
Target Allocation 9.00% 9.00%
Actual Allocation 12.00% 12.00%
Georgia Power | Pension plans | Private Credit    
Assets:    
Plan assets $ 8  
Target Allocation 3.00%  
Actual Allocation 0.00%  
Georgia Power | Pension plans | Infrastructure    
Assets:    
Plan assets $ 0  
Target Allocation 2.00%  
Actual Allocation 0.00%  
Georgia Power | Other postretirement benefit plans    
Assets:    
Plan assets $ 409 $ 368
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Georgia Power | Other postretirement benefit plans | Equity    
Assets:    
Target Allocation 58.00% 58.00%
Actual Allocation 57.00% 56.00%
Georgia Power | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets $ 53 $ 52
Georgia Power | Other postretirement benefit plans | International equity    
Assets:    
Plan assets $ 56 $ 56
Georgia Power | Other postretirement benefit plans | Fixed income    
Assets:    
Target Allocation 35.00% 35.00%
Actual Allocation 35.00% 34.00%
Georgia Power | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 16 $ 10
Georgia Power | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 14 12
Georgia Power | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 47 40
Georgia Power | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 13 9
Georgia Power | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 176 154
Georgia Power | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets $ 18 $ 19
Target Allocation 3.00% 4.00%
Actual Allocation 4.00% 5.00%
Georgia Power | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets $ 2 $ 2
Target Allocation 1.00% 1.00%
Actual Allocation 1.00% 1.00%
Georgia Power | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets $ 14 $ 14
Target Allocation 2.00% 2.00%
Actual Allocation 3.00% 4.00%
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans    
Assets:    
Plan assets $ 1,451 $ 1,572
Derivatives   (1)
Total   1,571
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Domestic equity    
Assets:    
Plan assets 611 651
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | International equity    
Assets:    
Plan assets 609 678
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 116 125
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Real estate investments    
Assets:    
Plan assets 115 118
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans    
Assets:    
Plan assets 80 76
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 47 46
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 16 17
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 13 9
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 4 4
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Georgia Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans    
Assets:    
Plan assets 2,001 1,688
Derivatives   0
Total   1,688
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Domestic equity    
Assets:    
Plan assets 241 217
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | International equity    
Assets:    
Plan assets 329 342
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 617 460
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 14 9
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Corporate bonds    
Assets:    
Plan assets 539 468
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Pooled funds    
Assets:    
Plan assets 243 190
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 18 2
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Georgia Power | Significant Other Observable Inputs (Level 2) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans    
Assets:    
Plan assets 299 261
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 6 6
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 40 39
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 16 10
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 14 12
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 47 40
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 176 154
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 0 0
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Georgia Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans    
Assets:    
Plan assets 0 0
Derivatives   0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Georgia Power | Significant Unobservable Inputs (Level 3) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans    
Assets:    
Plan assets 1,163 1,188
Derivatives   0
Total   1,188
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Real estate investments    
Assets:    
Plan assets 527 591
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Special situations    
Assets:    
Plan assets 77 59
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private equity    
Assets:    
Plan assets 551 538
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private Credit    
Assets:    
Plan assets 8  
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans    
Assets:    
Plan assets 30 31
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Trust-owned life insurance    
Assets:    
Plan assets 0 0
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 14 15
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 2 2
Georgia Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 14 14
Mississippi Power | Pension plans    
Assets:    
Plan assets $ 675 $ 648
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Mississippi Power | Pension plans | Equity    
Assets:    
Target Allocation 41.00% 45.00%
Actual Allocation 40.00% 43.00%
Mississippi Power | Pension plans | Domestic equity    
Assets:    
Plan assets $ 124 $ 127
Mississippi Power | Pension plans | International equity    
Assets:    
Plan assets $ 137 $ 149
Mississippi Power | Pension plans | Fixed income    
Assets:    
Target Allocation 30.00% 30.00%
Actual Allocation 32.00% 28.00%
Mississippi Power | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 90 $ 67
Mississippi Power | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 2 1
Mississippi Power | Pension plans | Corporate bonds    
Assets:    
Plan assets 79 68
Mississippi Power | Pension plans | Pooled funds    
Assets:    
Plan assets 36 28
Mississippi Power | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 20 18
Mississippi Power | Pension plans | Real estate investments    
Assets:    
Plan assets $ 94 $ 103
Target Allocation 12.00% 13.00%
Actual Allocation 14.00% 15.00%
Mississippi Power | Pension plans | Special situations    
Assets:    
Plan assets $ 11 $ 9
Target Allocation 3.00% 3.00%
Actual Allocation 2.00% 2.00%
Mississippi Power | Pension plans | Private equity    
Assets:    
Plan assets $ 81 $ 78
Target Allocation 9.00% 9.00%
Actual Allocation 12.00% 12.00%
Mississippi Power | Pension plans | Private Credit    
Assets:    
Plan assets $ 1  
Target Allocation 3.00%  
Actual Allocation 0.00%  
Mississippi Power | Pension plans | Infrastructure    
Assets:    
Plan assets $ 0  
Target Allocation 2.00%  
Actual Allocation 0.00%  
Mississippi Power | Other postretirement benefit plans    
Assets:    
Plan assets $ 24 $ 24
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Mississippi Power | Other postretirement benefit plans | Equity    
Assets:    
Target Allocation 34.00% 37.00%
Actual Allocation 33.00% 35.00%
Mississippi Power | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets $ 4 $ 4
Mississippi Power | Other postretirement benefit plans | International equity    
Assets:    
Plan assets $ 4 $ 5
Mississippi Power | Other postretirement benefit plans | Fixed income    
Assets:    
Target Allocation 43.00% 43.00%
Actual Allocation 44.00% 41.00%
Mississippi Power | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 7 $ 4
Mississippi Power | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 2 2
Mississippi Power | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 1 1
Mississippi Power | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 1 2
Mississippi Power | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets $ 3 $ 4
Target Allocation 10.00% 11.00%
Actual Allocation 11.00% 12.00%
Mississippi Power | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets $ 0 $ 0
Target Allocation 2.00% 2.00%
Actual Allocation 2.00% 2.00%
Mississippi Power | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets $ 2 $ 2
Target Allocation 7.00% 7.00%
Actual Allocation 10.00% 10.00%
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans    
Assets:    
Plan assets $ 212 $ 229
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Domestic equity    
Assets:    
Plan assets 89 95
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | International equity    
Assets:    
Plan assets 89 99
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 17 18
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Real estate investments    
Assets:    
Plan assets 17 17
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans    
Assets:    
Plan assets 8 9
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 3 3
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 3 3
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 1 2
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 1 1
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Mississippi Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans    
Assets:    
Plan assets 293 246
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Domestic equity    
Assets:    
Plan assets 35 32
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | International equity    
Assets:    
Plan assets 48 50
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 90 67
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 2 1
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Corporate bonds    
Assets:    
Plan assets 79 68
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Pooled funds    
Assets:    
Plan assets 36 28
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 3 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Mississippi Power | Significant Other Observable Inputs (Level 2) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans    
Assets:    
Plan assets 12 10
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 1 1
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 1 2
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 7 4
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 2 2
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 1 1
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Mississippi Power | Significant Unobservable Inputs (Level 3) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans    
Assets:    
Plan assets 170 173
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Real estate investments    
Assets:    
Plan assets 77 86
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Special situations    
Assets:    
Plan assets 11 9
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private equity    
Assets:    
Plan assets 81 78
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private Credit    
Assets:    
Plan assets 1  
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans    
Assets:    
Plan assets 4 5
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 2 3
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Special situations    
Assets:    
Plan assets 0 0
Mississippi Power | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 2 2
Southern Power | Pension plans    
Assets:    
Plan assets $ 187 $ 177
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Southern Power | Pension plans | Equity    
Assets:    
Target Allocation 41.00% 45.00%
Actual Allocation 40.00% 43.00%
Southern Power | Pension plans | Domestic equity    
Assets:    
Plan assets $ 34 $ 34
Southern Power | Pension plans | International equity    
Assets:    
Plan assets $ 38 $ 41
Southern Power | Pension plans | Fixed income    
Assets:    
Target Allocation 30.00% 30.00%
Actual Allocation 32.00% 28.00%
Southern Power | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 25 $ 18
Southern Power | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 1  
Southern Power | Pension plans | Corporate bonds    
Assets:    
Plan assets 22 19
Southern Power | Pension plans | Pooled funds    
Assets:    
Plan assets 10 8
Southern Power | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 6 5
Southern Power | Pension plans | Real estate investments    
Assets:    
Plan assets $ 26 $ 29
Target Allocation 12.00% 13.00%
Actual Allocation 14.00% 15.00%
Southern Power | Pension plans | Special situations    
Assets:    
Plan assets $ 3 $ 2
Target Allocation 3.00% 3.00%
Actual Allocation 2.00% 2.00%
Southern Power | Pension plans | Private equity    
Assets:    
Plan assets $ 22 $ 21
Target Allocation 9.00% 9.00%
Actual Allocation 12.00% 12.00%
Southern Power | Pension plans | Private Credit    
Assets:    
Plan assets $ 0  
Target Allocation 3.00%  
Actual Allocation 0.00%  
Southern Power | Pension plans | Infrastructure    
Assets:    
Plan assets $ 0  
Target Allocation 2.00%  
Actual Allocation 0.00%  
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans    
Assets:    
Plan assets $ 59 $ 62
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Domestic equity    
Assets:    
Plan assets 24 25
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | International equity    
Assets:    
Plan assets 25 27
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0  
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 5 5
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Real estate investments    
Assets:    
Plan assets 5 5
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Southern Power | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans    
Assets:    
Plan assets 82 68
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Domestic equity    
Assets:    
Plan assets 10 9
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | International equity    
Assets:    
Plan assets 13 14
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 25 18
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 1  
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Corporate bonds    
Assets:    
Plan assets 22 19
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Pooled funds    
Assets:    
Plan assets 10 8
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 1 0
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Southern Power | Significant Other Observable Inputs (Level 2) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0  
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Southern Power | Significant Unobservable Inputs (Level 3) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans    
Assets:    
Plan assets 46 47
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0  
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Real estate investments    
Assets:    
Plan assets 21 24
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Special situations    
Assets:    
Plan assets 3 2
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private equity    
Assets:    
Plan assets 22 21
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Southern Power | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Company Gas | Pension plans    
Assets:    
Plan assets $ 989 $ 1,001
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Southern Company Gas | Pension plans | Equity    
Assets:    
Target Allocation 41.00% 45.00%
Actual Allocation 40.00% 43.00%
Southern Company Gas | Pension plans | Domestic equity    
Assets:    
Plan assets $ 182 $ 195
Southern Company Gas | Pension plans | International equity    
Assets:    
Plan assets $ 201 $ 229
Southern Company Gas | Pension plans | Fixed income    
Assets:    
Target Allocation 30.00% 30.00%
Actual Allocation 32.00% 28.00%
Southern Company Gas | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 132 $ 104
Southern Company Gas | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 3 2
Southern Company Gas | Pension plans | Corporate bonds    
Assets:    
Plan assets 116 105
Southern Company Gas | Pension plans | Pooled funds    
Assets:    
Plan assets 52 43
Southern Company Gas | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 29 29
Southern Company Gas | Pension plans | Real estate investments    
Assets:    
Plan assets $ 138 $ 160
Target Allocation 12.00% 13.00%
Actual Allocation 14.00% 15.00%
Southern Company Gas | Pension plans | Special situations    
Assets:    
Plan assets $ 16 $ 13
Target Allocation 3.00% 3.00%
Actual Allocation 2.00% 2.00%
Southern Company Gas | Pension plans | Private equity    
Assets:    
Plan assets $ 118 $ 121
Target Allocation 9.00% 9.00%
Actual Allocation 12.00% 12.00%
Southern Company Gas | Pension plans | Private Credit    
Assets:    
Plan assets $ 2  
Target Allocation 3.00%  
Actual Allocation 0.00%  
Southern Company Gas | Pension plans | Infrastructure    
Assets:    
Plan assets $ 0  
Target Allocation 2.00%  
Actual Allocation 0.00%  
Southern Company Gas | Other postretirement benefit plans    
Assets:    
Plan assets $ 127 $ 113
Target Allocation 100.00% 100.00%
Actual Allocation 100.00% 100.00%
Southern Company Gas | Other postretirement benefit plans | Equity    
Assets:    
Target Allocation 72.00% 72.00%
Actual Allocation 72.00% 70.00%
Southern Company Gas | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets $ 69 $ 58
Southern Company Gas | Other postretirement benefit plans | International equity    
Assets:    
Plan assets $ 24 $ 22
Southern Company Gas | Other postretirement benefit plans | Fixed income    
Assets:    
Target Allocation 26.00% 26.00%
Actual Allocation 26.00% 27.00%
Southern Company Gas | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets $ 1 $ 1
Southern Company Gas | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 1 1
Southern Company Gas | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 29 27
Southern Company Gas | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 1 1
Southern Company Gas | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets $ 1 $ 2
Target Allocation 1.00% 1.00%
Actual Allocation 1.00% 2.00%
Southern Company Gas | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets $ 1 $ 1
Target Allocation 1.00% 1.00%
Actual Allocation 1.00% 1.00%
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans    
Assets:    
Plan assets $ 310 $ 353
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Domestic equity    
Assets:    
Plan assets 130 146
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | International equity    
Assets:    
Plan assets 130 152
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 25 28
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Real estate investments    
Assets:    
Plan assets 25 27
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans    
Assets:    
Plan assets 5 5
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 2 2
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 2 2
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 1 1
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 0 0
Southern Company Gas | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans    
Assets:    
Plan assets 430 381
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Domestic equity    
Assets:    
Plan assets 52 49
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | International equity    
Assets:    
Plan assets 71 77
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 132 104
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 3 2
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Corporate bonds    
Assets:    
Plan assets 116 105
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Pooled funds    
Assets:    
Plan assets 52 43
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 4 1
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans    
Assets:    
Plan assets 120 105
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 67 56
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 22 20
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 1 1
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 1 1
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 29 27
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Other Observable Inputs (Level 2) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Real estate investments    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Special situations    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Private equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Private Credit    
Assets:    
Plan assets 0  
Southern Company Gas | Significant Unobservable Inputs (Level 3) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans    
Assets:    
Plan assets 249 267
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Domestic equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | International equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Mortgage- and asset-backed securities    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Real estate investments    
Assets:    
Plan assets 113 133
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Special situations    
Assets:    
Plan assets 16 13
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private equity    
Assets:    
Plan assets 118 121
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Private Credit    
Assets:    
Plan assets 2  
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Pension plans | Infrastructure    
Assets:    
Plan assets 0  
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans    
Assets:    
Plan assets 2 3
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Domestic equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | International equity    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | U.S. Treasury, government, and agency bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Corporate bonds    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Pooled funds    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Cash equivalents and other    
Assets:    
Plan assets 0 0
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Real estate investments    
Assets:    
Plan assets 1 2
Southern Company Gas | Net Asset Value as a Practical Expedient (NAV) | Other postretirement benefit plans | Private equity    
Assets:    
Plan assets $ 1 $ 1