FINANCING ACTIVITIES - Schedule of Interest Income Earned for Funds Loaned to Utility Money Pool (Details) - Utility - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
APCo
Short-Term Debt [Line Items]
Interest Income Earned on Advances to the Money Pool	$ 1	$ 2	$ 1
I&M
Short-Term Debt [Line Items]
Interest Income Earned on Advances to the Money Pool	3	0	2
OPCo
Short-Term Debt [Line Items]
Interest Income Earned on Advances to the Money Pool	1	3	0
PSO
Short-Term Debt [Line Items]
Interest Income Earned on Advances to the Money Pool	2	1	2
Nonutility | AEP Texas
Short-Term Debt [Line Items]
Interest Income Earned on Advances to the Money Pool	1	4	0
Nonutility | SWEPCo
Short-Term Debt [Line Items]
Interest Income Earned on Advances to the Money Pool	3	0	0
Direct Borrowing | AEPTCo
Short-Term Debt [Line Items]
Interest Income Earned on Advances to the Money Pool	$ 4	$ 11	$ 7