FINANCING - Notes Payable (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Amount Outstanding	$ 1,338	$ 2,314
Weighted Average Interest Rate	4.80%	5.70%
Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 1,138	$ 1,794
Weighted Average Interest Rate	4.70%	5.60%
Short-term bank debt
Short-term Debt [Line Items]
Amount Outstanding	$ 200	$ 520
Weighted Average Interest Rate	5.30%	6.40%
Alabama Power
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 40
Alabama Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 40
Weighted Average Interest Rate	0.00%	5.50%
Georgia Power
Short-term Debt [Line Items]
Amount Outstanding	$ 200	$ 1,329
Weighted Average Interest Rate	5.30%	5.90%
Georgia Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 809
Weighted Average Interest Rate	0.00%	5.60%
Georgia Power | Short-term bank debt
Short-term Debt [Line Items]
Amount Outstanding	$ 200	$ 520
Weighted Average Interest Rate	5.30%	6.40%
Southern Power
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 138
Southern Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 138
Weighted Average Interest Rate	0.00%	5.50%
Southern Company Gas
Short-term Debt [Line Items]
Amount Outstanding	$ 455	$ 415
Southern Company Gas | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 455	$ 415
Weighted Average Interest Rate	4.70%	5.50%
Southern Company Gas Capital | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 283	$ 23
Weighted Average Interest Rate	4.70%	5.50%
Nicor Gas | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 172	$ 392
Weighted Average Interest Rate	4.60%	5.50%
Mississippi Power
Short-term Debt [Line Items]
Amount Outstanding	$ 14	$ 0
Mississippi Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 14	$ 0
Weighted Average Interest Rate	4.60%	0.00%