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REGULATORY MATTERS - MPC Fuel Cost Recovery and Ad Valorem Tax Adjustment (Details) - Mississippi Power - USD ($) $ in Millions |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Feb. 06, 2024 | Jul. 31, 2024 | Jun. 30, 2023 | Jul. 31, 2022 | Jun. 30, 2022 | Feb. 28, 2022 | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2021 | Oct. 31, 2024 | Oct. 31, 2023
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount |  | $ (5) | $ (7) |  | $ 18 |  |  |  |  | $ 9 |  |
Ad Valorem Tax Adjustment |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount |  |  |  | $ 5 |  |  |  |  |  |  |  |
Retail electric revenues |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount | $ 18 |  |  |  |  | $ 43 |  |  |  |  |  |
Over (under) recovered fuel cost |  |  |  |  |  |  |  | $ (32) | $ (50) |  | $ (25) | $ (61)
Retail ECM |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Over (under) recovered fuel cost |  |  |  |  |  |  |  | 32 | 27 |  |  |
MRA Revenue |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount |  |  |  |  |  |  |  | 4 | 22 |  |  |
Over (under) recovered fuel cost |  |  |  |  |  |  |  | $ 19 | $ (5) |  |  |
MRA Revenue | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount |  |  |  |  |  |  | $ (19) |  |  |  |  |

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- Definition Amount of public utility's approved rate increase (decrease) by regulatory agency. + References No definition available. + Details
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