INCOME TAXES - Operating Loss Carryforwards (Details) $ in Millions	Dec. 31, 2024 USD ($)
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	$ 110.3
OHIO POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	2.7
PUBLIC SERVICE COMPANY OF OKLAHOMA
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	27.8
SOUTHWESTERN ELECTRIC POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	36.1
Arkansas
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	273.9
Arkansas | SOUTHWESTERN ELECTRIC POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	273.5
Colorado
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	70.5
Illinois
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	53.9
Kentucky
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	186.7
Louisiana
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	644.8
Louisiana | SOUTHWESTERN ELECTRIC POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	634.5
Michigan
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	30.9
Ohio Municipal
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	2,155.8
Ohio Municipal | OHIO POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	93.7
Oklahoma
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	889.8
Oklahoma | PUBLIC SERVICE COMPANY OF OKLAHOMA
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	1,010.0
Pennsylvania
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	61.2
Tennessee
Effective Income Tax Rate Reconciliation [Line Items]
State net income tax operating loss carryforward	$ 46.1