Regulatory Matters - Schedule of Cost Recovery Clauses (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Loss Contingencies [Line Items]
Natural gas cost under recovery	$ 361	$ 266
ALABAMA POWER CO | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Rate CNP Compliance	29	16
Rate CNP PPA	93	84
Retail Energy Cost Recovery	191	126
ALABAMA POWER CO | Other regulatory assets, current
Loss Contingencies [Line Items]
Retail Energy Cost Recovery	60	0
GEORGIA POWER CO | Other deferred charges and assets
Loss Contingencies [Line Items]
Fuel Cost Recovery	948	410
MISSISSIPPI POWER CO | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Ad Valorem Tax	29	37
MISSISSIPPI POWER CO | Other customer accounts receivable
Loss Contingencies [Line Items]
Fuel Cost Recovery	29	4
MISSISSIPPI POWER CO | Other regulatory assets, current
Loss Contingencies [Line Items]
Ad Valorem Tax	12	12
SOUTHERN Co GAS
Loss Contingencies [Line Items]
Natural gas cost under recovery	361	266
SOUTHERN Co GAS | Other regulatory assets, deferred
Loss Contingencies [Line Items]
Natural gas cost under recovery	15	207
SOUTHERN Co GAS | Other regulatory assets, current
Loss Contingencies [Line Items]
Natural gas cost under recovery	$ 361	$ 266