Regulatory Matters - Schedule of Cost Recovery Clauses (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
ALABAMA POWER CO | Other regulatory assets, current
Loss Contingencies [Line Items]
Rate ECR	$ 62	$ 0
ALABAMA POWER CO | Other regulatory liabilities, current
Loss Contingencies [Line Items]
Rate ECR	0	29
GEORGIA POWER CO | Receivables – under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	655	713
GEORGIA POWER CO | Deferred under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	325	453
MISSISSIPPI POWER CO | Wholesale MB
Loss Contingencies [Line Items]
Fuel Cost Recovery	0	0
MISSISSIPPI POWER CO | Deferred under recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	0	32
MISSISSIPPI POWER CO | Receivables – customer accounts, net
Loss Contingencies [Line Items]
Fuel Cost Recovery	28	0
MISSISSIPPI POWER CO | Over recovered retail fuel clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	0	32
MISSISSIPPI POWER CO | Other current liabilities | Wholesale MRA
Loss Contingencies [Line Items]
Fuel Cost Recovery	5	19
SOUTHERN Co GAS | Natural gas cost over recovery
Loss Contingencies [Line Items]
Natural gas cost under recovery	$ 107	$ 193