Introduction - Schedule of Other Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Subject to amortization:
Gross Carrying Amount	$ 669	$ 669
Accumulated Amortization	(403)	(376)
Other Intangible Assets, Net	266	293
Not subject to amortization:
FCC licenses	75	75
Total other intangible assets
Gross Carrying Amount	744	744
Accumulated Amortization	(403)	(376)
Other Intangible Assets, Net	341	368
Customer relationships
Subject to amortization:
Gross Carrying Amount	212	212
Accumulated Amortization	(179)	(172)
Other Intangible Assets, Net	33	40
Total other intangible assets
Accumulated Amortization	(179)	(172)
Trade names
Subject to amortization:
Gross Carrying Amount	64	64
Accumulated Amortization	(58)	(53)
Other Intangible Assets, Net	6	11
Total other intangible assets
Accumulated Amortization	(58)	(53)
PPA fair value adjustments
Subject to amortization:
Gross Carrying Amount	390	390
Accumulated Amortization	(163)	(148)
Other Intangible Assets, Net	227	242
Total other intangible assets
Accumulated Amortization	(163)	(148)
Other
Subject to amortization:
Gross Carrying Amount	3	3
Accumulated Amortization	(3)	(3)
Other Intangible Assets, Net	0	0
Total other intangible assets
Accumulated Amortization	(3)	(3)
SOUTHERN POWER CO
Subject to amortization:
Accumulated Amortization	(163)	(148)
Total other intangible assets
Accumulated Amortization	(163)	(148)
SOUTHERN POWER CO | PPA fair value adjustments
Subject to amortization:
Gross Carrying Amount	390	390
Accumulated Amortization	(163)	(148)
Other Intangible Assets, Net	227	242
Total other intangible assets
Accumulated Amortization	(163)	(148)
SOUTHERN Co GAS
Subject to amortization:
Gross Carrying Amount	182	182
Accumulated Amortization	(171)	(166)
Other Intangible Assets, Net	11	16
Total other intangible assets
Accumulated Amortization	(171)	(166)
Other Intangible Assets, Net	11	16
SOUTHERN Co GAS | Customer relationships
Subject to amortization:
Gross Carrying Amount	156	156
Accumulated Amortization	(149)	(145)
Other Intangible Assets, Net	7	11
Total other intangible assets
Accumulated Amortization	(149)	(145)
SOUTHERN Co GAS | Trade names
Subject to amortization:
Gross Carrying Amount	26	26
Accumulated Amortization	(22)	(21)
Other Intangible Assets, Net	4	5
Total other intangible assets
Accumulated Amortization	$ (22)	$ (21)