v3.26.3
REVENUE FROM CONTRACTS WITH CUSTOMERS - Affiliate Accounts Receivable (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
AEP Texas    
Disaggregation of Revenue [Line Items]    
Affiliated Companies $ 14 $ 15
AEP Texas | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 1 0
AEPTCo    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 161 153
AEPTCo | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 157 146
APCo    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 176 142
APCo | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 149 113
I&M    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 102 90
I&M | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 83 67
OPCo    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 126 132
OPCo | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 90 74
PSO    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 53 45
PSO | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 35 22
SWEPCo    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 84 91
SWEPCo | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies $ 48 $ 65