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ASSET RETIREMENT OBLIGATIONS - Accumulated Provisions for the External Decommissioning Trust Funds (Details) - External decommissioning trust funds - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Georgia Power |  |
Public Utilities, General Disclosures [Line Items] |  |
Accumulated provisions for decommissioning | $ 1,217 | $ 1,145
Plant Farley | Alabama Power |  |
Public Utilities, General Disclosures [Line Items] |  |
Accumulated provisions for decommissioning | 1,324 | 1,156
Plant Hatch | Georgia Power |  |
Public Utilities, General Disclosures [Line Items] |  |
Accumulated provisions for decommissioning | 757 | 716
Plant Vogtle Units 1 and 2 | Georgia Power |  |
Public Utilities, General Disclosures [Line Items] |  |
Accumulated provisions for decommissioning | $ 460 | $ 429

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