v3.26.3
BENEFIT PLANS - Qualified Pension Contribution (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Jun. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Defined Benefit Plan Disclosure [Line Items]      
Qualified Pension Plan $ 95 $ 0 $ 95
AEP Texas      
Defined Benefit Plan Disclosure [Line Items]      
Qualified Pension Plan 12 $ 0 $ 12
APCo      
Defined Benefit Plan Disclosure [Line Items]      
Qualified Pension Plan 0    
I&M      
Defined Benefit Plan Disclosure [Line Items]      
Qualified Pension Plan 2    
PSO      
Defined Benefit Plan Disclosure [Line Items]      
Qualified Pension Plan 1    
SWEPCo      
Defined Benefit Plan Disclosure [Line Items]      
Qualified Pension Plan $ 9