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CONTINGENCIES, COMMITMENTS, AND GUARANTEES - MPC Other Matters (Details) - USD ($) |  | 12 Months Ended | 60 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jan. 01, 2019 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2025 | Jan. 15, 2024 | Dec. 31, 2016 | Dec. 31, 2010
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Period costs |  | $ 26,000,000 | $ 19,000,000 |  |  |  |  |  |
Mississippi Power |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Period costs |  | 0 | 0 |  |  |  |  |  |
Kemper County energy facility assets, net | Mississippi Power |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Pre-tax charge to income |  | 11,000,000 | 4,000,000 | $ 24,000,000 |  |  |  |  |
After tax charge to income |  | $ 8,000,000 | $ 3,000,000 |  |  |  |  |  |
Government grants expected |  |  |  |  |  |  |  | $ 137,000,000 | $ 270,000,000
Government grants received |  |  |  |  | $ 387,000,000 |  |  |  |
Scenario, Forecast | Kemper County energy facility assets, net | Mississippi Power | Minimum |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Period costs |  |  |  |  |  | $ 10,000,000 |  |  |
Scenario, Forecast | Kemper County energy facility assets, net | Mississippi Power | Maximum |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Period costs |  |  |  |  |  | $ 20,000,000 |  |  |
Scenario, Forecast | Plant Daniel | Mississippi Power |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Payments to acquire businesses |  |  |  |  |  |  | $ 1 |  |
Business combination, option to purchase, period |  |  |  |  |  |  | 120 days |  |
Scenario, Forecast | Plant Daniel | Gulf Power |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Undivided ownership interest to be restructured |  |  |  |  |  |  | 50.00% |  |
Percent ownership in individual unit |  |  |  |  |  |  | 100.00% |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Gulf Power |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |
Proceeds from divestiture of businesses, amount held back | $ 75,000,000 |  |  |  |  |  |  |  |

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