PROPERTY, PLANT, AND EQUIPMENT - Deferred Cloud Implementation Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	$ 19,069	$ 20,148
Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	325	345
Amortization	46	29	$ 0
Alabama Power
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	5,090	5,372
Alabama Power | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	85	81
Amortization	11	8	0
Georgia Power
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	10,200	11,117
Georgia Power | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	99	108
Amortization	19	12	0
Mississippi Power
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	887	828
Mississippi Power | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	13	14
Amortization	0	0	0
Southern Power
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	998	956
Southern Power | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	15	18
Amortization	0	0	0
Southern Company Gas
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	890	882
Southern Company Gas | Deferred Cloud Implementation Costs
Property, Plant and Equipment [Line Items]
Total deferred charges and other assets	43	54
Amortization	$ 8	$ 0	$ 0