RELATED PARTY TRANSACTIONS - Transmission Service Charges (Details) - Net Transmission Services - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
AEP TEXAS INC.
Related Party Transaction [Line Items]
Related party transaction, amount	$ 30.6	$ 28.7	$ 28.5
APPALACHIAN POWER COMPANY
Related Party Transaction [Line Items]
Related party transaction, amount	380.7	365.1	345.1
INDIANA MICHIGAN POWER COMPANY
Related Party Transaction [Line Items]
Related party transaction, amount	252.7	226.2	220.8
OHIO POWER COMPANY
Related Party Transaction [Line Items]
Related party transaction, amount	696.1	665.3	608.2
PUBLIC SERVICE COMPANY OF OKLAHOMA
Related Party Transaction [Line Items]
Related party transaction, amount	127.1	100.1	110.8
SOUTHWESTERN ELECTRIC POWER COMPANY
Related Party Transaction [Line Items]
Related party transaction, amount	$ 64.5	$ 49.2	$ 62.1