INCOME TAXES - Tax Credit Carryforwards (Details) $ in Millions	Dec. 31, 2024 USD ($)
Federal
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	$ 197.9
Federal | INDIANA MICHIGAN POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	37.5
Federal | PUBLIC SERVICE COMPANY OF OKLAHOMA
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	26.5
Federal | SOUTHWESTERN ELECTRIC POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	31.7
State and Local Government
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	40.2
State and Local Government | INDIANA MICHIGAN POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	0.0
State and Local Government | PUBLIC SERVICE COMPANY OF OKLAHOMA
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	40.2
State and Local Government | SOUTHWESTERN ELECTRIC POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Tax credit carryforward	$ 0.0