PROPERTY, PLANT, AND EQUIPMENT - Additional Information (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Regulatory asset amortization period	4 years
Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Amortization	$ 46	$ 29	$ 0
Alabama Power | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Amortization	11	8	0
Georgia Power | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Amortization	19	12	0
Southern Company Gas | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Amortization	8	0	0
SOUTHERN POWER CO | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Amortization	0	0	0
Mississippi Power | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Amortization	$ 0	$ 0	$ 0
Plant Farley | Alabama Power | Nuclear Outage
Property, Plant and Equipment [Line Items]
Regulatory asset amortization period	18 months
Plant Hatch Units 1 and 2 | Georgia Power | Nuclear Outage | Maximum
Property, Plant and Equipment [Line Items]
Regulatory asset amortization period	24 months
Plant Vogtle Nuclear Units One , Two, and Three | Georgia Power | Nuclear Outage
Property, Plant and Equipment [Line Items]
Regulatory asset amortization period	18 months