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Regulatory Matters - MPC (Details) $ in Millions | Jun. 13, 2024 USD ($) | May 07, 2024 USD ($) | Apr. 11, 2024 USD ($) | Mar. 29, 2024 USD ($) | Jun. 30, 2024 USD ($) | Apr. 26, 2024 MW
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Loss Contingencies [Line Items] |  |  |  |  |  |
Minimum annual accrual, amount |  |  | $ 12 |  |  |
MISSISSIPPI POWER CO |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Approved rate increase (decrease) |  |  | $ 13 |  |  |
MISSISSIPPI POWER CO | Plant Watson Unit 4 |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Required fossil-stream generation retirements (in MWs) | MW |  |  |  |  |  | 268
MISSISSIPPI POWER CO | Plant Greene County Units 1 and 2 |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Required fossil-stream generation retirements (in MWs) | MW |  |  |  |  |  | 206
Proportionate ownership share |  |  |  |  |  | 40.00%
MISSISSIPPI POWER CO | Plant Daniel Units 1 and 2 |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Required fossil-stream generation retirements (in MWs) | MW |  |  |  |  |  | 502
Proportionate ownership share |  |  |  |  |  | 50.00%
Remaining net book value |  |  |  |  | $ 480 |
MISSISSIPPI POWER CO | Ad Valorem Tax Adjustment |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Requested rate increase (decrease) amount | $ (5) | $ 8 |  |  |  |
MISSISSIPPI POWER CO | Municipal And Rural Associations Tariff |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Requested rate increase (decrease) amount |  |  |  | $ 8 |  |

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