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RATE MATTERS - I&M Rate Matters (Details) - INDIANA MICHIGAN POWER COMPANY - USD ($) $ in Millions | 1 Months Ended |
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Jan. 31, 2025 | Jul. 31, 2024 | Mar. 31, 2024 | Dec. 31, 2023 | Sep. 30, 2023 | Aug. 31, 2023 | Nov. 30, 2024
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Earning test, over-earning credit to customers |  |  |  |  |  |  | $ 18.0
Subsequent Event |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Earning test, over-earning credit to customers, proposed | $ 21.0 |  |  |  |  |  |
2023 Michigan Power Supply Cost Recovery | Minimum |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Public utilities, recommended disallowance purchased power |  |  | $ 3.0 |  |  |  |
2023 Michigan Power Supply Cost Recovery | Maximum |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Public utilities, recommended disallowance purchased power |  |  | $ 15.0 |  |  |  |
2023 Indiana Base Rate Case |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Requested annual increase |  |  |  |  |  | $ 116.0 |
Requested return on equity |  |  |  |  |  | 10.50% |
Requested debt capital structure |  |  |  |  |  | 48.80% |
Requested equity capital structure |  |  |  |  |  | 51.20% |
Amount of increased depreciation expense requested |  |  |  |  |  | $ 41.0 |
Requested deferred storm costs |  |  |  |  |  | $ 15.0 |
Settlement agreement annual increase step one |  |  |  | $ 28.0 |  |  |
Settlement agreement annual increase step two |  |  |  | $ 34.0 |  |  |
Settlement agreement return on common equity |  |  |  | 9.85% |  |  |
Settlement agreement equity capital structure |  |  |  | 50.00% |  |  |
Settlement agreement debt capital structure |  |  |  | 50.00% |  |  |
Settlement agreement adjusted equity capital structure |  |  |  | 51.20% |  |  |
Settlement agreement increase related to depreciation expense |  |  |  | $ 25.0 |  |  |
Settlement agreement increase related to storm expense |  |  |  | $ 11.0 |  |  |
2023 Indiana Base Rate Case | Subsequent Event |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Approved annual base rate increase | $ 15.0 |  |  |  |  |  |
2023 Michigan Base Rate Case |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Requested annual increase |  |  |  |  | $ 34.0 |  |
Requested return on equity |  |  |  |  | 10.50% |  |
Requested debt capital structure |  |  |  |  | 49.40% |  |
Requested equity capital structure |  |  |  |  | 50.60% |  |
Amount of increased depreciation expense requested |  |  |  |  | $ 11.0 |  |
Approved annual base rate increase |  | $ 17.0 |  |  |  |  |
Approved return on equity |  | 9.86% |  |  |  |  |
Approved debt capital structure |  | 52.00% |  |  |  |  |
Approved equity capital structure |  | 48.00% |  |  |  |  |

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