SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 669	$ 669
Accumulated Amortization	(412)	(376)
Other Intangible Assets, Net	257	293
Intangible assets, gross	744	744
Intangible assets, net	332	368
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	(182)	(172)
Other Intangible Assets, Net	30	40
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	64	64
Accumulated Amortization	(59)	(53)
Other Intangible Assets, Net	5	11
PPA fair value adjustments
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	390	390
Accumulated Amortization	(168)	(148)
Other Intangible Assets, Net	222	242
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3	3
Accumulated Amortization	(3)	(3)
Other Intangible Assets, Net	0	0
Southern Power
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	(168)	(148)
Southern Power | PPA fair value adjustments
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	390	390
Accumulated Amortization	(168)	(148)
Other Intangible Assets, Net	222	242
Southern Company Gas
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	182	182
Accumulated Amortization	(173)	(166)
Other Intangible Assets, Net	9	16
Intangible assets, net	9	16
Southern Company Gas | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		156
Accumulated Amortization	(150)	(145)
Other Intangible Assets, Net	6	11
Southern Company Gas | Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		26
Accumulated Amortization	(23)	(21)
Other Intangible Assets, Net	$ 3	$ 5