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FAIR VALUE MEASUREMENTS - Summary of Nuclear Trust Investments (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | $ 4,395.1 | $ 3,860.2
Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 2,297.8 | 1,902.9
Gross unrealized losses | (15.5) | (10.0)
Other than temporary impairments | (26.0) | (41.8)
INDIANA MICHIGAN POWER COMPANY |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 4,395.1 | 3,860.2
INDIANA MICHIGAN POWER COMPANY | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 2,297.8 | 1,902.9
Gross unrealized losses | (15.5) | (10.0)
Other than temporary impairments | (26.0) | (41.8)
Cash and Cash Equivalents |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 23.3 | 16.8
Cash and Cash Equivalents | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 0.0 | 0.0
Gross unrealized losses | 0.0 | 0.0
Other than temporary impairments | 0.0 | 0.0
Cash and Cash Equivalents | INDIANA MICHIGAN POWER COMPANY |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 23.3 | 16.8
Cash and Cash Equivalents | INDIANA MICHIGAN POWER COMPANY | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 0.0 | 0.0
Gross unrealized losses | 0.0 | 0.0
Other than temporary impairments | 0.0 | 0.0
United States Government |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 1,322.8 | 1,273.0
United States Government | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 8.2 | 28.6
Gross unrealized losses | (5.3) | (3.9)
Other than temporary impairments | (20.2) | (33.2)
United States Government | INDIANA MICHIGAN POWER COMPANY |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 1,322.8 | 1,273.0
United States Government | INDIANA MICHIGAN POWER COMPANY | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 8.2 | 28.6
Gross unrealized losses | (5.3) | (3.9)
Other than temporary impairments | (20.2) | (33.2)
Corporate Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 211.3 | 132.1
Corporate Debt | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 0.7 | 4.8
Gross unrealized losses | (9.8) | (5.2)
Other than temporary impairments | (5.8) | (8.6)
Corporate Debt | INDIANA MICHIGAN POWER COMPANY |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 211.3 | 132.1
Corporate Debt | INDIANA MICHIGAN POWER COMPANY | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 0.7 | 4.8
Gross unrealized losses | (9.8) | (5.2)
Other than temporary impairments | (5.8) | (8.6)
State and Local Government |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 0.0 | 1.7
State and Local Government | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 0.0 | 0.0
Gross unrealized losses | 0.0 | 0.0
Other than temporary impairments | 0.0 | 0.0
State and Local Government | INDIANA MICHIGAN POWER COMPANY |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 0.0 | 1.7
State and Local Government | INDIANA MICHIGAN POWER COMPANY | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 0.0 | 0.0
Gross unrealized losses | 0.0 | 0.0
Other than temporary impairments | 0.0 | 0.0
Subtotal Fixed Income Securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 1,534.1 | 1,406.8
Subtotal Fixed Income Securities | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 8.9 | 33.4
Gross unrealized losses | (15.1) | (9.1)
Other than temporary impairments | (26.0) | (41.8)
Subtotal Fixed Income Securities | INDIANA MICHIGAN POWER COMPANY |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 1,534.1 | 1,406.8
Subtotal Fixed Income Securities | INDIANA MICHIGAN POWER COMPANY | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 8.9 | 33.4
Gross unrealized losses | (15.1) | (9.1)
Other than temporary impairments | (26.0) | (41.8)
Equity Securities - Domestic |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 2,837.7 | 2,436.6
Equity Securities - Domestic | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 2,288.9 | 1,869.5
Gross unrealized losses | (0.4) | (0.9)
Other than temporary impairments | 0.0 | 0.0
Equity Securities - Domestic | INDIANA MICHIGAN POWER COMPANY |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value | 2,837.7 | 2,436.6
Equity Securities - Domestic | INDIANA MICHIGAN POWER COMPANY | Spent Nuclear Fuel and Decommissioning Trusts |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Gross unrealized gains | 2,288.9 | 1,869.5
Gross unrealized losses | (0.4) | (0.9)
Other than temporary impairments | $ 0.0 | $ 0.0

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