FINANCING - Notes Payable (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Short-term Debt [Line Items]
Amount Outstanding	$ 722	$ 1,338
Weighted Average Interest Rate	3.90%	4.80%
Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 722	$ 1,138
Weighted Average Interest Rate	3.90%	4.70%
Short-term bank debt
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 200
Weighted Average Interest Rate	0.00%	5.30%
Georgia Power
Short-term Debt [Line Items]
Amount Outstanding	$ 160	$ 200
Weighted Average Interest Rate	3.90%	5.30%
Georgia Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 160	$ 0
Weighted Average Interest Rate	3.90%	0.00%
Georgia Power | Short-term bank debt
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 200
Weighted Average Interest Rate	0.00%	5.30%
Southern Power
Short-term Debt [Line Items]
Amount Outstanding	$ 138	$ 0
Southern Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 138	$ 0
Weighted Average Interest Rate	3.90%	0.00%
Southern Company Gas
Short-term Debt [Line Items]
Amount Outstanding	$ 425	$ 455
Southern Company Gas | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 425	$ 455
Weighted Average Interest Rate	3.90%	4.70%
Southern Company Gas Capital | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 209	$ 283
Weighted Average Interest Rate	3.90%	4.70%
Nicor Gas | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 216	$ 172
Weighted Average Interest Rate	3.90%	4.60%
Mississippi Power
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 14
Mississippi Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 14
Weighted Average Interest Rate	0.00%	4.60%