Regulatory Matters - Schedule of Cost Recovery Clauses (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
ALABAMA POWER CO | Other regulatory assets, current
Loss Contingencies [Line Items]
Rate CNP Compliance	$ 8	$ 8
Rate CNP PPA	18	18
ALABAMA POWER CO | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Rate CNP Compliance	19	25
Rate CNP PPA	82	85
ALABAMA POWER CO | Deferred under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Rate ECR	173	246
GEORGIA POWER CO | Receivables – under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	679	694
GEORGIA POWER CO | Deferred under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	1,044	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	13	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	20	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	10	5
SOUTHERN Co GAS | Natural gas cost over recovery
Loss Contingencies [Line Items]
Natural gas cost under recovery	$ 150	$ 214