Regulatory Matters - Schedule of Cost Recovery Clauses (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
ALABAMA POWER CO | Other regulatory assets, current
Loss Contingencies [Line Items]
Rate CNP Compliance	$ 0	$ 8
Rate CNP PPA	18	18
ALABAMA POWER CO | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Rate CNP Compliance	0	25
Rate CNP PPA	70	85
ALABAMA POWER CO | Other regulatory liabilities, current
Loss Contingencies [Line Items]
Rate CNP Compliance	4	0
ALABAMA POWER CO | Other regulatory liabilities, deferred
Loss Contingencies [Line Items]
Rate CNP Compliance	2	0
ALABAMA POWER CO | Deferred under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Rate ECR	10	246
GEORGIA POWER CO | Receivables – under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	683	694
GEORGIA POWER CO | Deferred under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	632	1,211
MISSISSIPPI POWER CO | Wholesale MB
Loss Contingencies [Line Items]
Fuel Cost Recovery	0	0
MISSISSIPPI POWER CO | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Ad Valorem Tax	14	12
MISSISSIPPI POWER CO | Deferred under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	0	50
MISSISSIPPI POWER CO | Receivables – customer accounts, net
Loss Contingencies [Line Items]
Fuel Cost Recovery	6	0
MISSISSIPPI POWER CO | Over recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	0	27
MISSISSIPPI POWER CO | Other current liabilities | Wholesale MRA
Loss Contingencies [Line Items]
Fuel Cost Recovery	16	5
SOUTHERN Co GAS | Natural gas cost over recovery
Loss Contingencies [Line Items]
Natural gas cost under recovery	$ 226	$ 214