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REGULATORY MATTERS - MPC Environmental Compliance Overview Plan (Details) - Mississippi Power - USD ($) $ in Millions |  |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Feb. 14, 2025 | Feb. 13, 2025 | Oct. 25, 2024 | Jul. 31, 2024 | May 31, 2024 | Jun. 30, 2023 | Apr. 30, 2023 | Jun. 30, 2022 | Apr. 30, 2022 | Dec. 31, 2021
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount |  |  |  | $ (5) |  | $ (7) |  | $ 18 |  | $ 9
Requested rate increase (decrease), amount |  |  | $ 11 |  |  |  |  |  |  |
Subsequent Event |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease), amount |  | $ 8 |  |  |  |  |  |  |  |
Environmental Compliance Overview Plan |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount |  |  |  |  | $ 9 |  | $ 3 |  | $ 1 |
Environmental Compliance Overview Plan | Subsequent Event |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease), amount | $ 6 |  |  |  |  |  |  |  |  |

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