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ASSET RETIREMENT OBLIGATIONS - Narrative (Details) |  | 1 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Aug. 01, 2023 USD ($) | Nov. 30, 2023 USD ($) | Sep. 30, 2023 USD ($) | Jun. 30, 2023 USD ($) | Dec. 31, 2022 USD ($) ashPond | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) ashPond | Dec. 31, 2019 USD ($) | Feb. 14, 2024 USD ($) | Mar. 06, 2023 USD ($) | Dec. 31, 2021 USD ($)
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revision to ARO |  |  |  |  |  | $ (399,000,000) | $ (834,000,000) |  |  |  |
Asset retirement obligations |  |  |  |  | $ 10,840,000,000 | 10,317,000,000 | 10,840,000,000 |  |  |  | $ 11,687,000,000
Plant Vogtle Units 3 and 4 |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Asset retirement obligations |  |  |  |  |  |  |  |  |  | $ 90,000,000 |
Plant Vogtle Unit 4 | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Asset retirement obligations |  |  |  |  |  |  |  |  | $ 118,000,000 |  |
Alabama Power |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revision to ARO |  |  |  |  |  | (15,000,000) | 0 |  |  |  |
Asset retirement obligations |  |  |  |  | 4,287,000,000 | $ 4,158,000,000 | 4,287,000,000 |  |  |  | 4,334,000,000
Asset Retirement Obligation, Period Increase (Decrease) |  |  |  | $ 15,000,000 |  |  |  |  |  |  |
Estimated inflation rate |  |  |  |  |  | 4.50% |  |  |  |  |
Estimated trust earnings rate |  |  |  |  |  | 7.00% |  |  |  |  |
Alabama Power | Internal reserves |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Accumulated provisions for decommissioning |  |  |  |  | $ 14,000,000 | $ 13,000,000 | 14,000,000 |  |  |  |
Alabama Power | Plant Farley |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Site-specific estimate of decommissioning costs, period of updates made |  |  |  |  |  | 5 years |  |  |  |  |
Georgia Power |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revision to ARO |  |  |  |  |  | $ (385,000,000) | $ (844,000,000) |  |  |  |
Number of ash ponds | ashPond |  |  |  |  | 1 |  | 1 |  |  |  |
Asset retirement obligations |  |  |  |  | $ 6,034,000,000 | $ 5,665,000,000 | $ 6,034,000,000 |  |  |  | 6,824,000,000
Asset Retirement Obligation, Period Increase (Decrease) |  | $ 210,000,000 | $ 175,000,000 |  |  |  |  |  |  |  |
Estimated inflation rate |  |  |  |  |  | 2.50% |  |  |  |  |
Estimated trust earnings rate |  |  |  |  |  | 4.50% |  |  |  |  |
Georgia Power | CCR AROs |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revision to ARO |  |  |  |  | (780,000,000) |  |  |  |  |  |
Georgia Power | Plant Hatch and Plant Vogtle Units 1 And 2 |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Annual decommissioning cost for ratemaking |  |  |  |  |  |  | 0 | $ 4,000,000 |  |  |
Georgia Power | Plant Vogtle Units 3 and 4 |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimated inflation rate |  |  |  |  |  | 2.40% |  |  |  |  |
Estimated trust earnings rate |  |  |  |  |  | 4.40% |  |  |  |  |
Annual decommissioning cost for ratemaking | $ 8,000,000 |  |  |  |  |  |  |  |  |  |
Mississippi Power |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revision to ARO |  |  |  |  |  | $ 2,000,000 | 3,000,000 |  |  |  |
Asset retirement obligations |  |  |  |  | $ 179,000,000 | $ 168,000,000 | $ 179,000,000 |  |  |  | $ 190,000,000

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