RELATED PARTY TRANSACTIONS - Transmission Service Charges (Details) - Net Transmission Services - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
AEP Texas
Related Party Transaction [Line Items]
Related party transaction, amount	$ 31	$ 31	$ 29
APCo
Related Party Transaction [Line Items]
Related party transaction, amount	440	381	365
I&M
Related Party Transaction [Line Items]
Related party transaction, amount	269	253	226
OPCo
Related Party Transaction [Line Items]
Related party transaction, amount	789	696	665
PSO
Related Party Transaction [Line Items]
Related party transaction, amount	171	127	100
SWEPCo
Related Party Transaction [Line Items]
Related party transaction, amount	$ 84	$ 65	$ 49