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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

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