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REGULATORY MATTERS - APC Rate NDR (Details) - Alabama Power - USD ($) | 12 Months Ended |
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Jan. 01, 2021
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Minimum natural disaster reserve balance, triggering establishment charge |  |  | $ 50,000,000 |  |  |
Natural disaster reserve authorized limit |  |  | $ 75,000,000 |  |  | $ 50,000,000
Maximum period for recovery deferred stock related operations and maintenance costs and any future reserve deficits |  |  | 24 months |  |  |
Maximum rate NDR charge per month, monthly nonresidential customer account |  |  | $ 10 |  |  |
Maximum rate NDR charge per month, monthly residential customer account |  |  | 5 |  |  |
Additional accruals authorized by state PSCs |  |  | 65,000,000 | $ 100,000,000 | $ 84,000,000 |
Annual recovery amount |  |  | 6,000,000 | 5,000,000 | $ 16,000,000 |
Regulatory asset, amortization period |  |  | $ 103,000,000 | $ 77,000,000 |  |
Scenario, Forecast |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
NDR, expected recovery amount | $ 3,000,000 | $ 8,000,000 |  |  |  |

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