BENEFIT PLANS - Schedule of Accumulated Benefit Obligation (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 3,604	$ 3,649
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	3,559	3,602
Nonqualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	45	47
AEP TEXAS INC.
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	305	303
AEP TEXAS INC. | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	303	301
AEP TEXAS INC. | Nonqualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	2	2
APPALACHIAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	433	434
APPALACHIAN POWER COMPANY | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	433	434
APPALACHIAN POWER COMPANY | Nonqualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	0	0
INDIANA MICHIGAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	419	423
INDIANA MICHIGAN POWER COMPANY | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	418	422
INDIANA MICHIGAN POWER COMPANY | Nonqualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	1	1
OHIO POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	319	326
OHIO POWER COMPANY | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	319	326
OHIO POWER COMPANY | Nonqualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	0	0
PUBLIC SERVICE COMPANY OF OKLAHOMA
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	174	176
PUBLIC SERVICE COMPANY OF OKLAHOMA | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	173	175
PUBLIC SERVICE COMPANY OF OKLAHOMA | Nonqualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	1	1
SOUTHWESTERN ELECTRIC POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	213	211
SOUTHWESTERN ELECTRIC POWER COMPANY | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	212	210
SOUTHWESTERN ELECTRIC POWER COMPANY | Nonqualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 1	$ 1