PROPERTY, PLANT, AND EQUIPMENT - Composite Straight-Line Rates (Details) - Utility plant in service	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Alabama Power
Property, Plant and Equipment [Line Items]
Composite rate	4.10%	2.70%	2.70%
Georgia Power
Property, Plant and Equipment [Line Items]
Composite rate	3.80%	3.30%	3.30%
Mississippi Power
Property, Plant and Equipment [Line Items]
Composite rate	3.40%	3.40%	3.60%
Southern Company Gas
Property, Plant and Equipment [Line Items]
Composite rate	2.70%	2.70%	2.80%