FAIR VALUE MEASUREMENTS - Narrative (Details) - Spent Nuclear Fuel and Decommissioning Trusts - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjusted cost of debt securities	$ 1,500	$ 1,400
Adjusted cost of equity securities	549	568
INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjusted cost of debt securities	1,500	1,400
Adjusted cost of equity securities	$ 549	$ 568