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REGULATORY MATTERS - MPC Environmental Compliance Overview Plan (Details) - USD ($) $ in Millions |  |  |  | 1 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 07, 2021 | Jun. 08, 2021 | Apr. 06, 2021 | Mar. 31, 2020 | Dec. 31, 2021 | Dec. 31, 2019
Mississippi Power |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Public utilities, approved rate increase (decrease), amount | $ 9.0 | $ 16.0 | $ 28.0 | $ (16.7) |  |
Mississippi Power | Environmental Compliance Overview Plan |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Percent ownership |  |  |  |  |  | 50.00%
Public utilities, requested cost to complete environmental compliance projects |  |  |  |  |  | $ 67.0
Public utilities, approved rate increase (decrease), amount |  | $ (9.0) |  |  |  |
Mississippi Power | Environmental Compliance Overview Plan | Property, Plant and Equipment |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Public utilities, requested cost to complete environmental compliance projects |  |  |  |  | $ 20.0 |
Mississippi Power | Environmental Compliance Overview Plan | Construction in Progress |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Public utilities, requested cost to complete environmental compliance projects |  |  |  |  | 14.0 |
Mississippi Power And Gulf Power | Environmental Compliance Overview Plan |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Public utilities, requested cost to complete environmental compliance projects |  |  |  |  |  | $ 125.0
Ash Pond | Mississippi Power | Environmental Compliance Overview Plan |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Public utilities, requested cost to complete environmental compliance projects |  |  |  |  | $ 13.0 |

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