BENEFIT PLANS - Schedule of Obligations in Excess of Fair Values Projected Benefit Obligation (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	$ 3,843	$ 3,872
Fair Value of Plan Assets	3,759	3,666
Underfunded Projected Benefit Obligation	(84)	(206)
AEP TEXAS INC.
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	327	323
Fair Value of Plan Assets	303	288
Underfunded Projected Benefit Obligation	(24)	(35)
APPALACHIAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	0	1
Fair Value of Plan Assets	0	0
Underfunded Projected Benefit Obligation	0	(1)
INDIANA MICHIGAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	1	1
Fair Value of Plan Assets	0	0
Underfunded Projected Benefit Obligation	(1)	(1)
OHIO POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	1	0
Fair Value of Plan Assets	0	0
Underfunded Projected Benefit Obligation	(1)	0
PUBLIC SERVICE COMPANY OF OKLAHOMA
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	2	1
Fair Value of Plan Assets	0	0
Underfunded Projected Benefit Obligation	(2)	(1)
SOUTHWESTERN ELECTRIC POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	233	228
Fair Value of Plan Assets	200	189
Underfunded Projected Benefit Obligation	$ (33)	$ (39)