FINANCING - Notes Payable (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Amount Outstanding	$ 2,314	$ 2,609
Weighted Average Interest Rate	5.70%	4.90%
Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 1,794	$ 809
Weighted Average Interest Rate	5.60%	4.70%
Short-term bank debt
Short-term Debt [Line Items]
Amount Outstanding	$ 520	$ 1,800
Weighted Average Interest Rate	6.40%	5.00%
Alabama Power
Short-term Debt [Line Items]
Amount Outstanding	$ 40	$ 0
Alabama Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 40	$ 0
Weighted Average Interest Rate	5.50%	0.00%
Georgia Power
Short-term Debt [Line Items]
Amount Outstanding	$ 1,329	$ 1,600
Weighted Average Interest Rate	5.90%	5.00%
Georgia Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 809	$ 0
Weighted Average Interest Rate	5.60%	0.00%
Georgia Power | Short-term bank debt
Short-term Debt [Line Items]
Amount Outstanding	$ 520	$ 1,600
Weighted Average Interest Rate	6.40%	5.00%
Southern Power
Short-term Debt [Line Items]
Amount Outstanding	$ 138	$ 225
Southern Power | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 138	$ 225
Weighted Average Interest Rate	5.50%	4.70%
Southern Company Gas
Short-term Debt [Line Items]
Amount Outstanding	$ 415	$ 768
Southern Company Gas | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 415	$ 768
Weighted Average Interest Rate	5.50%	4.70%
Southern Company Gas Capital | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 23	$ 285
Weighted Average Interest Rate	5.50%	4.80%
Nicor Gas | Commercial paper
Short-term Debt [Line Items]
Amount Outstanding	$ 392	$ 283
Weighted Average Interest Rate	5.50%	4.60%
Nicor Gas | Short-term bank debt
Short-term Debt [Line Items]
Amount Outstanding	$ 0	$ 200
Weighted Average Interest Rate	0.00%	4.90%