v3.26.3
FINANCING ACTIVITIES - Repayments and Retirements of Debt (Details) - USD ($)
$ in Millions
 1 Months Ended 9 Months Ended
Mar. 31, 2026
Sep. 30, 2026
Sep. 30, 2025
Debt Instrument [Line Items]      
Principal Amount Paid   $ 1,834 $ 2,804
AEP Texas      
Debt Instrument [Line Items]      
Principal Amount Paid   75 475
AEPTCo      
Debt Instrument [Line Items]      
Principal Amount Paid   623 90
APCo      
Debt Instrument [Line Items]      
Principal Amount Paid   206 498
I&M      
Debt Instrument [Line Items]      
Principal Amount Paid   94 270
PSO      
Debt Instrument [Line Items]      
Principal Amount Paid   50 $ 125
Other Long-term Debt | AEPTCo      
Debt Instrument [Line Items]      
Principal Amount Paid   623  
Other Long-term Debt | APCo      
Debt Instrument [Line Items]      
Principal Amount Paid   175  
3.20% Pollution Control Bonds | Pollution Control Bonds      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 50  
Interest Rate   3.20%  
2.29% Securitization Bonds | Securitization Bonds | AEP Texas      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 25  
Interest Rate   2.29%  
3.81% Senior Unsecured Notes | Senior Unsecured Notes | AEP Texas      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 50  
Interest Rate   3.81%  
13.72% Other Long-term Debt | Other Long-term Debt | APCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 1  
Interest Rate   13.72%  
3.77% Securitization Bonds | Securitization Bonds | APCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 30  
Interest Rate   3.77%  
3.44% Notes Payable | Notes Payable | I&M      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 3  
Interest Rate   3.44%  
5.93% Notes Payable | Notes Payable | I&M      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 3  
Interest Rate   5.93%  
6.01% Notes Payable | Notes Payable | I&M      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 16  
Interest Rate   6.01%  
6.41% Notes Payable | Notes Payable | I&M      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 13  
Interest Rate   6.41%  
4.89% Notes Payable | Notes Payable | I&M      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 29  
Interest Rate   4.89%  
Variable Note Payable | Notes Payable | I&M      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 30  
3.05% Senior Unsecured Notes | Senior Unsecured Notes | PSO      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 50  
Interest Rate   3.05%  
4.88% Securitization Bonds | Securitization Bonds | SWEPCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 17  
Interest Rate   4.88%  
1.65% Senior Unsecured Notes | Senior Unsecured Notes | SWEPCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 500  
Interest Rate   1.65%  
4.70% Pollution Control Bonds | Pollution Control Bonds | KPCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 65  
Interest Rate   4.70%  
5.30% Securitization Bonds | Securitization Bonds | KPCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 16  
Interest Rate   5.30%  
4.18% Senior Unsecured Notes | Senior Unsecured Notes | KPCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 120  
Interest Rate   4.18%  
2.75 % Senior Unsecured Notes | Senior Unsecured Notes | Transource Energy      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 3  
Interest Rate   2.75%  
6.89% Notes Payable | Notes Payable | WPCo      
Debt Instrument [Line Items]      
Principal Amount Paid   $ 15  
Interest Rate   6.89%  
4.24% Notes Payable | Notes Payable | SWEPCo | Related Party      
Debt Instrument [Line Items]      
Principal Amount Paid $ 1,000    
Interest Rate 4.24%