BENEFIT PLANS - Schedule of Matching Contribution Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	$ 84	$ 82	$ 88
AEP TEXAS INC.
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	7	7	7
APPALACHIAN POWER COMPANY
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	8	8	8
INDIANA MICHIGAN POWER COMPANY
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	11	11	11
OHIO POWER COMPANY
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	8	8	8
PUBLIC SERVICE COMPANY OF OKLAHOMA
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	6	5	5
SOUTHWESTERN ELECTRIC POWER COMPANY
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	$ 6	$ 7	$ 7