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CONTINGENCIES, COMMITMENTS, AND GUARANTEES - MPC and Traditional Electric Operating Companies Other Matters (Details) - USD ($) $ in Millions | 12 Months Ended | 60 Months Ended
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2025
Loss Contingencies [Line Items] |  |  |  |
Period costs | $ 130 | $ 90 |  |
Mississippi Power |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Period costs | 0 | 0 |  |
Alabama Power |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Period costs | 8 | 0 |  |
Kemper County energy facility assets, net | Mississippi Power |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Pre-tax charge to income | 12 | 17 | $ 15 |
After tax charge to income | $ 9 | $ 12 | $ 12 |
Scenario, Forecast | Kemper County energy facility assets, net | Mississippi Power | Maximum |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Period costs |  |  |  | $ 15

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