v3.26.1
Derivatives - Schedule of Derivative Category and Balance Sheet Location (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized $ 74 $ 93
Gross amounts offset (39) (21)
Derivative asset, net amounts recognized in the balance sheets 35 72
Derivative liability, gross amount recognized 434 321
Gross amounts offset (57) (54)
Derivative liability, net amounts recognized in the balance sheets 377 267
Collateral already posted, assets, aggregate fair value 18  
Interest rate derivatives    
Derivatives, Fair Value [Line Items]    
Derivative liability, net amounts recognized in the balance sheets 31  
Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 6 6
Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 4 6
Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 58 55
Derivative liability, gross amount recognized 149 99
Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 28 24
Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 89 64
Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 30 31
Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 60 35
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 10 32
Derivative liability, gross amount recognized 281 216
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 3 1
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 12 6
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 2 2
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 1 1
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 5 8
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 52 48
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 0
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 153 139
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 17
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 23 22
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 4
Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 40 0
ALABAMA POWER CO    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 27 19
Gross amounts offset (16) (13)
Derivative asset, net amounts recognized in the balance sheets 11 6
Derivative liability, gross amount recognized 58 31
Gross amounts offset (16) (13)
Derivative liability, net amounts recognized in the balance sheets 42 18
Collateral already posted, assets, aggregate fair value 0  
ALABAMA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 27 19
Derivative liability, gross amount recognized 56 31
ALABAMA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 15 9
ALABAMA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 12 10
ALABAMA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 31 18
ALABAMA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 25 13
ALABAMA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 0
ALABAMA POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 2 0
GEORGIA POWER CO    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 14 18
Gross amounts offset (11) (14)
Derivative asset, net amounts recognized in the balance sheets 3 4
Derivative liability, gross amount recognized 48 33
Gross amounts offset (11) (14)
Derivative liability, net amounts recognized in the balance sheets 37 19
GEORGIA POWER CO | Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 2 1
GEORGIA POWER CO | Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 0 0
GEORGIA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 12 17
Derivative liability, gross amount recognized 48 33
GEORGIA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 5 7
GEORGIA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 7 10
GEORGIA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 32 23
GEORGIA POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 16 10
MISSISSIPPI POWER CO    
Derivatives, Fair Value [Line Items]    
Gross amounts offset (13) (13)
Derivative asset, net amounts recognized in the balance sheets 1 1
Gross amounts offset (13) (13)
Derivative liability, net amounts recognized in the balance sheets 27 14
MISSISSIPPI POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 14 14
Derivative liability, gross amount recognized 40 27
MISSISSIPPI POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 3 3
MISSISSIPPI POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 11 11
MISSISSIPPI POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 21 15
MISSISSIPPI POWER CO | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 19 12
SOUTHERN POWER CO    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 3 21
Gross amounts offset (1) 0
Derivative asset, net amounts recognized in the balance sheets 2 21
Derivative liability, gross amount recognized 4 1
Gross amounts offset (1) 0
Derivative liability, net amounts recognized in the balance sheets 3 1
Collateral already posted, assets, aggregate fair value 0  
SOUTHERN POWER CO | Energy-related derivatives    
Derivatives, Fair Value [Line Items]    
Derivative liability, net amounts recognized in the balance sheets 0  
SOUTHERN POWER CO | Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 1
SOUTHERN POWER CO | Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 1 0
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 3 20
Derivative liability, gross amount recognized 3 1
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 1 1
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 2 2
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 2 1
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 1 0
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 17
SOUTHERN POWER CO | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Foreign currency derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 0 0
SOUTHERN Co GAS    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 11 9
Gross amounts offset 6 19
Derivative asset, net amounts recognized in the balance sheets 17 28
Derivative liability, gross amount recognized 78 79
Gross amounts offset (12) (14)
Derivative liability, net amounts recognized in the balance sheets 66 65
Collateral already posted, assets, aggregate fair value 18 33
SOUTHERN Co GAS | Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 4 4
SOUTHERN Co GAS | Energy-related derivatives not designated as hedging instruments | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 3 6
SOUTHERN Co GAS | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 5 5
SOUTHERN Co GAS | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 5 8
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 2 0
Derivative liability, gross amount recognized 70 65
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 2 0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 8 5
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Energy-related derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 0 1
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative asset, gross amount recognized 0 0
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized 13 13
SOUTHERN Co GAS | Derivatives designated as hedging instruments in cash flow and fair value hedges | Energy-related derivatives designated as hedging instruments for regulatory purposes | Interest rate derivatives | Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Derivative liability, gross amount recognized $ 49 $ 46