INCOME TAXES - Income Taxes Paid (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	$ 18	$ 59
Transfer Credits	(64)	(17)
Total Cash Paid/(Received)	(46)	42
AEP TEXAS INC.
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(9)	(8)
Transfer Credits	0	0
Total Cash Paid/(Received)	(9)	(8)
AEP TRANSMISSION COMPANY, LLC
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	85	(21)
Transfer Credits	0	0
Total Cash Paid/(Received)	85	(21)
APPALACHIAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(46)	(19)
Transfer Credits	(4)	0
Total Cash Paid/(Received)	(50)	(19)
INDIANA MICHIGAN POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	106	3
Transfer Credits	(50)	0
Total Cash Paid/(Received)	56	3
OHIO POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(40)	1
Transfer Credits	0	0
Total Cash Paid/(Received)	(40)	1
PUBLIC SERVICE COMPANY OF OKLAHOMA
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(31)	(4)
Transfer Credits	(6)	(9)
Total Cash Paid/(Received)	(37)	(13)
SOUTHWESTERN ELECTRIC POWER COMPANY
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(28)	(28)
Transfer Credits	(3)	(9)
Total Cash Paid/(Received)	$ (31)	$ (37)