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REGULATORY MATTERS - MPC Performance Evaluation Plan (Details) - Mississippi Power $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jul. 31, 2024 USD ($) | Jun. 30, 2023 USD ($) | Jun. 30, 2022 USD ($) | Dec. 31, 2024 scale filing | Dec. 31, 2021 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Scale of performance evaluation | scale |  |  |  | 10 |
Performance evaluation plan, number of filings per calendar year | filing |  |  |  | 2 |
Public utilities, approved rate increase (decrease), amount | $ | $ (5) | $ (7) | $ 18 |  | $ 9
Approved rate decrease, percent |  |  | (1.90%) |  |
Weighted Average | Measurement Input, Average Customer Price |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Performance evaluation plan, measurement input |  |  |  | 0.40 |
Weighted Average | Measurement Input, Service Reliability |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Performance evaluation plan, measurement input |  |  |  | 0.40 |
Weighted Average | Measurement Input, Customer Satisfaction |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Performance evaluation plan, measurement input |  |  |  | 0.20 |

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