FINANCING ACTIVITIES - Schedule of Direct Borrowing Activity (Details) - Direct Borrowing - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
AEPTCo
Short-Term Debt [Line Items]
Maximum Borrowings	$ 107	$ 49
Maximum Loans	153	149
Average Borrowings	18	15
Average Loans	54	57
Borrowings	0	0
Loans	70	20
Authorized Short-term Borrowing Limit	0	0
SWTCo
Short-Term Debt [Line Items]
Maximum Borrowings	2	2
Maximum Loans	0	0
Average Borrowings	2	2
Average Loans	0	0
Borrowings	2	2
Loans	0	0
Authorized Short-term Borrowing Limit	50	$ 50
Midwest Transmission Holdings
Short-Term Debt [Line Items]
Maximum Borrowings	0
Maximum Loans	36
Average Borrowings	0
Average Loans	4
Borrowings	0
Loans	0
Authorized Short-term Borrowing Limit	$ 0