SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 671	$ 677
Accumulated Amortization	(340)	(307)
Other Intangible Assets, Net	331	370
Intangible assets, gross	746	752
Intangible assets, net	406	445
FCC licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	75	75
Accumulated Amortization	0	0
Other Intangible Assets, Net	75	75
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	212	212
Accumulated Amortization	(162)	(150)
Other Intangible Assets, Net	50	62
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	64	64
Accumulated Amortization	(44)	(38)
Other Intangible Assets, Net	20	26
PPA fair value adjustments
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	390	390
Accumulated Amortization	(129)	(109)
Other Intangible Assets, Net	261	281
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5	11
Accumulated Amortization	(5)	(10)
Other Intangible Assets, Net	0	1
Southern Power
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	(129)	(109)
Southern Power | PPA fair value adjustments
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	390	390
Accumulated Amortization	(129)	(109)
Other Intangible Assets, Net	261	281
Southern Company Gas
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	182	182
Accumulated Amortization	(156)	(145)
Other Intangible Assets, Net	26	37
Intangible assets, net	26	37
Southern Company Gas | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	156	156
Accumulated Amortization	(139)	(130)
Other Intangible Assets, Net	17	26
Southern Company Gas | Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	26	26
Accumulated Amortization	(17)	(15)
Other Intangible Assets, Net	$ 9	$ 11