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