v3.26.3
FAIR VALUE MEASUREMENTS - Debt Fair Value (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value $ 52,541 $ 47,322
Fair Value 47,152 44,930
AEP Texas    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value 7,686 7,016
Fair Value 6,748 6,586
AEPTCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value 6,837 6,599
Fair Value 5,553 5,812
APCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value 7,422 6,259
Fair Value 6,928 6,147
I&M    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value 4,118 3,561
Fair Value 3,542 3,288
OPCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value 3,721 3,718
Fair Value 3,121 3,331
PSO    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value 4,462 3,526
Fair Value 4,003 3,349
SWEPCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Book Value 5,591 4,974
Fair Value $ 4,906 $ 4,603