REVENUE FROM CONTRACTS WITH CUSTOMERS - Affiliate Accounts Receivable (Details) - Related Party - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
AEP Texas
Disaggregation of Revenue [Line Items]
Affiliated Companies	$ 0.0	$ 0.0
AEPTCo
Disaggregation of Revenue [Line Items]
Affiliated Companies	141.0	131.6
APCo
Disaggregation of Revenue [Line Items]
Affiliated Companies	82.4	83.7
I&M
Disaggregation of Revenue [Line Items]
Affiliated Companies	57.1	55.0
OPCo
Disaggregation of Revenue [Line Items]
Affiliated Companies	65.1	63.6
PSO
Disaggregation of Revenue [Line Items]
Affiliated Companies	13.3	13.0
SWEPCo
Disaggregation of Revenue [Line Items]
Affiliated Companies	$ 19.5	$ 21.4