SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 669	$ 671
Accumulated Amortization	(376)	(340)
Other Intangible Assets, Net	293	331
Intangible assets, gross	744	746
Intangible assets, net	368	406
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	(172)	(162)
Other Intangible Assets, Net	40	50
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	64	64
Accumulated Amortization	(53)	(44)
Other Intangible Assets, Net	11	20
PPA fair value adjustments
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	390	390
Accumulated Amortization	(148)	(129)
Other Intangible Assets, Net	242	261
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3	5
Accumulated Amortization	(3)	(5)
Other Intangible Assets, Net	0	0
Southern Power
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	(148)	(129)
Southern Power | PPA fair value adjustments
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	390	390
Accumulated Amortization	(148)	(129)
Other Intangible Assets, Net	242	261
Southern Company Gas
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	182	182
Accumulated Amortization	(166)	(156)
Other Intangible Assets, Net	16	26
Intangible assets, net	16	26
Southern Company Gas | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	156	156
Accumulated Amortization	(145)	(139)
Other Intangible Assets, Net	11	17
Southern Company Gas | Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	26	26
Accumulated Amortization	(21)	(17)
Other Intangible Assets, Net	$ 5	$ 9