FINANCING ACTIVITIES - Repayments and Retirements of Debt (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2026	Mar. 31, 2025
Debt Instrument [Line Items]
Principal Amount Paid		$ 678	$ 229
AEP TEXAS INC.
Debt Instrument [Line Items]
Principal Amount Paid		12	12
AEP TRANSMISSION COMPANY, LLC
Debt Instrument [Line Items]
Principal Amount Paid		101	50
INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		31	27
APPALACHIAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 15	$ 14
Notes Payable | SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid	$ 1,000
Interest Rate	4.24%	4.24%
5.20% Senior Unsecured Notes | Senior Unsecured Notes | AEP TEXAS INC.
Debt Instrument [Line Items]
Interest Rate	5.20%	5.20%
5.20% Senior Unsecured Notes | Senior Unsecured Notes | SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Interest Rate	5.20%	5.20%
5.60% Senior Unsecured Notes | Senior Unsecured Notes | INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Interest Rate	5.60%	5.60%
5.30% Senior Unsecured Notes | Senior Unsecured Notes | SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Interest Rate	5.30%	5.30%
5.90% Senior Unsecured Notes | Senior Unsecured Notes | SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Interest Rate	5.90%	5.90%
2.29% Securitization Bonds | Securitization Bonds | AEP TEXAS INC.
Debt Instrument [Line Items]
Principal Amount Paid		$ 12
Interest Rate	2.29%	2.29%
Variable Other Long-term Debt | Other Long-term Debt | AEP TRANSMISSION COMPANY, LLC
Debt Instrument [Line Items]
Principal Amount Paid		$ 101
3.77% Securitization Bonds | Securitization Bonds | APPALACHIAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 15
Interest Rate	3.77%	3.77%
3.44% Notes Payable | Notes Payable | INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 1
Interest Rate	3.44%	3.44%
5.93% Notes Payable | Notes Payable | INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 1
Interest Rate	5.93%	5.93%
6.01% Notes Payable | Notes Payable | INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 5
Interest Rate	6.01%	6.01%
6.41% Notes Payable | Notes Payable | INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 4
Interest Rate	6.41%	6.41%
4.89% Notes Payable | Notes Payable | INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 10
Interest Rate	4.89%	4.89%
Variable Note Payable | Notes Payable | INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 10
1.65% Senior Unsecured Notes | Senior Unsecured Notes | SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 500
Interest Rate	1.65%	1.65%
4.88% Securitization Bonds | Securitization Bonds | SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 8
Interest Rate	4.88%	4.88%
5.30% Securitization Bonds | Securitization Bonds | Transource Energy
Debt Instrument [Line Items]
Principal Amount Paid		$ 9
Interest Rate	5.30%	5.30%
2.75 % Senior Unsecured Notes | Senior Unsecured Notes | Transource Energy
Debt Instrument [Line Items]
Principal Amount Paid		$ 2
Interest Rate	2.75%	2.75%