INCOME TAXES - Income Taxes Paid (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	$ 26	$ 60
Transfer Credits	(63)	(102)
Total Cash Paid/(Received)	(37)	(42)
AEP Texas
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(20)	33
Transfer Credits	0	0
Total Cash Paid/(Received)	(20)	33
AEPTCo
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	124	115
Transfer Credits	0	0
Total Cash Paid/(Received)	124	115
APCo
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(49)	76
Transfer Credits	(4)	0
Total Cash Paid/(Received)	(53)	76
I&M
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	116	1
Transfer Credits	(50)	0
Total Cash Paid/(Received)	66	1
OPCo
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(21)	53
Transfer Credits	0	0
Total Cash Paid/(Received)	(21)	53
PSO
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(32)	(86)
Transfer Credits	(6)	(48)
Total Cash Paid/(Received)	(38)	(134)
SWEPCo
Income Tax Paid, by Individual Jurisdiction [Line Items]
Income Taxes Paid/(Received)	(34)	(61)
Transfer Credits	(3)	(54)
Total Cash Paid/(Received)	$ (37)	$ (115)