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Regulatory Matters - MPC (Details) - USD ($) $ in Millions |  |  |  |  | 1 Months Ended
--- | --- | --- | --- | --- | ---
Jul. 31, 2023 | Apr. 04, 2023 | Apr. 03, 2023 | Mar. 31, 2023 | Jul. 31, 2022
Loss Contingencies [Line Items] |  |  |  |  |
Minimum annual accrual, amount |  |  | $ 8 |  |
MISSISSIPPI POWER CO |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Approved rate increase (decrease) |  | $ 12 |  |  |
MISSISSIPPI POWER CO | Ad Valorem Tax Adjustment |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Requested rate increase (decrease) amount |  |  |  | $ 7 |
MISSISSIPPI POWER CO | ECO Plan |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Approved rate increase (decrease) |  | $ 3 |  |  |
MISSISSIPPI POWER CO | Municipal And Rural Associations Tariff |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Requested rate increase (decrease) amount |  |  |  |  | $ 23
MISSISSIPPI POWER CO | Municipal And Rural Associations Tariff | Subsequent Event |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Requested rate increase (decrease) amount | $ 16 |  |  |  |
Customer refund payments | $ 6 |  |  |  |

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