v3.26.1
REVENUE FROM CONTRACTS WITH CUSTOMERS - Affiliate Accounts Receivable (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
AEP TRANSMISSION COMPANY, LLC    
Disaggregation of Revenue [Line Items]    
Affiliated Companies $ 177 $ 153
AEP TRANSMISSION COMPANY, LLC | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 173 146
APPALACHIAN POWER COMPANY    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 165 142
APPALACHIAN POWER COMPANY | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 137 113
INDIANA MICHIGAN POWER COMPANY    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 87 90
INDIANA MICHIGAN POWER COMPANY | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 64 67
OHIO POWER COMPANY    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 134 132
OHIO POWER COMPANY | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 73 74
PUBLIC SERVICE COMPANY OF OKLAHOMA    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 125 45
PUBLIC SERVICE COMPANY OF OKLAHOMA | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 128 22
SOUTHWESTERN ELECTRIC POWER COMPANY    
Disaggregation of Revenue [Line Items]    
Affiliated Companies 116 91
SOUTHWESTERN ELECTRIC POWER COMPANY | Related Party    
Disaggregation of Revenue [Line Items]    
Affiliated Companies $ 92 $ 65