BENEFIT PLANS - Schedule of Obligations in Excess of Fair Values Accumulated Benefit Obligation (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 45	$ 47
Fair Value of Plan Assets	0	0
Underfunded Accumulated Benefit Obligation	(45)	(47)
AEP TEXAS INC.
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	2	303
Fair Value of Plan Assets	0	288
Underfunded Accumulated Benefit Obligation	(2)	(15)
APPALACHIAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	0	0
Fair Value of Plan Assets	0	0
Underfunded Accumulated Benefit Obligation	0	0
INDIANA MICHIGAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	1	1
Fair Value of Plan Assets	0	0
Underfunded Accumulated Benefit Obligation	(1)	(1)
OHIO POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	0	0
Fair Value of Plan Assets	0	0
Underfunded Accumulated Benefit Obligation	0	0
PUBLIC SERVICE COMPANY OF OKLAHOMA
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	1	1
Fair Value of Plan Assets	0	0
Underfunded Accumulated Benefit Obligation	(1)	(1)
SOUTHWESTERN ELECTRIC POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	213	211
Fair Value of Plan Assets	200	189
Underfunded Accumulated Benefit Obligation	$ (13)	$ (22)