FINANCING ACTIVITIES - Repayments and Retirements of Debt (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Mar. 31, 2026	Jun. 30, 2026	Jun. 30, 2025
Debt Instrument [Line Items]
Principal Amount Paid		$ 1,578	$ 1,324
AEP TEXAS INC.
Debt Instrument [Line Items]
Principal Amount Paid		62	12
AEP TRANSMISSION COMPANY, LLC
Debt Instrument [Line Items]
Principal Amount Paid		613	90
APPALACHIAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		191	418
INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		63	$ 240
Other Long-term Debt \| AEP TRANSMISSION COMPANY, LLC
Debt Instrument [Line Items]
Principal Amount Paid		613
Other Long-term Debt \| APPALACHIAN POWER COMPANY
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 INC.
Debt Instrument [Line Items]
Principal Amount Paid		$ 12
Interest Rate		2.29%
3.81% Senior Unsecured Notes \| Senior Unsecured Notes \| AEP TEXAS INC.
Debt Instrument [Line Items]
Principal Amount Paid		$ 50
Interest Rate		3.81%
13.72% Other Long-term Debt \| Other Long-term Debt \| APPALACHIAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 1
Interest Rate		13.72%
3.77% Securitization Bonds \| Securitization Bonds \| APPALACHIAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 15
Interest Rate		3.77%
3.44% Notes Payable \| Notes Payable \| INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 2
Interest Rate		3.44%
5.93% Notes Payable \| Notes Payable \| INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 3
Interest Rate		5.93%
6.01% Notes Payable \| Notes Payable \| INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 10
Interest Rate		6.01%
6.41% Notes Payable \| Notes Payable \| INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 9
Interest Rate		6.41%
4.89% Notes Payable \| Notes Payable \| INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 19
Interest Rate		4.89%
Variable Note Payable \| Notes Payable \| INDIANA MICHIGAN POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 20
4.88% Securitization Bonds \| Securitization Bonds \| SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Principal Amount Paid		$ 8
Interest Rate		4.88%
1.65% Senior Unsecured Notes \| Senior Unsecured Notes \| SOUTHWESTERN ELECTRIC POWER COMPANY
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		$ 9
Interest Rate		5.30%
2.75 % Senior Unsecured Notes \| Senior Unsecured Notes \| Transource Energy
Debt Instrument [Line Items]
Principal Amount Paid		$ 2
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 \| SOUTHWESTERN ELECTRIC POWER COMPANY \| Related Party
Debt Instrument [Line Items]
Principal Amount Paid	$ 1,000
Interest Rate	4.24%