INCOME TAXES - Income Taxes Paid (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Paid, by Individual Jurisdiction [Line Items]
Federal	$ 70	$ 100	$ 38
Total To/(From) Tax Authority	103	133	78
Transfer Credits	(187)	(202)	(102)
Total Cash Paid/(Received)	(84)	(69)	(24)
AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
Federal	46	11	12
Total To/(From) Tax Authority	50	11	12
Transfer Credits	0	0	0
Total Cash Paid/(Received)	50	11	12
AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
Federal	191	43	87
Total To/(From) Tax Authority	214	43	88
Transfer Credits	0	0	0
Total Cash Paid/(Received)	214	43	88
APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Federal	88	48	47
Total To/(From) Tax Authority	105	48	47
Transfer Credits	0	0	0
Total Cash Paid/(Received)	105	48	47
INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Federal	23	17	93
Total To/(From) Tax Authority	43	24	109
Transfer Credits	0	0	0
Total Cash Paid/(Received)	43	24	109
OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Federal	62	19	39
Total To/(From) Tax Authority	62	19	39
Transfer Credits	0	0	0
Total Cash Paid/(Received)	62	19	39
PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
Proceeds from income tax refund, federal	(158)	(15)	(11)
Total To/(From) Tax Authority	(158)	(15)	(11)
Transfer Credits	(90)	(96)	(35)
Total Cash Paid/(Received)	(248)	(111)	(46)
SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Proceeds from income tax refund, federal	(91)	(15)	(41)
Total To/(From) Tax Authority	(90)	(15)	(41)
Transfer Credits	(97)	(89)	(41)
Total Cash Paid/(Received)	(187)	(104)	(82)
IN
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	16	7	16
IN | AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
IN | AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	11	0	0
IN | APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
IN | INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	14	7	16
IN | OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
IN | PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
IN | SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
OH
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			10
OH | AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			0
OH | AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			1
OH | APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			0
OH | INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			0
OH | OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			0
OH | PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			0
OH | SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:			0
MI
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0
MI | AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0
MI | AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0
MI | APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0
MI | INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	4
MI | OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0
MI | PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0
MI | SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0
TX
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	5		4
TX | AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	4		0
TX | AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0		0
TX | APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0		0
TX | INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0		0
TX | OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0		0
TX | PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0		0
TX | SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	1		0
WV
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	8	9
WV | AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0
WV | AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	11	0
WV | APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	17	0
WV | INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	1	0
WV | OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0
WV | PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0
WV | SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0
All Other
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	4	17	10
All Other | AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
All Other | AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	1	0	0
All Other | APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
All Other | INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	1	0	0
All Other | OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
All Other | PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	0	0	0
All Other | SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
State and Local:	$ 0	$ 0	$ 0