FINANCING ACTIVITIES - Issuances of Debt (Details) $ in Millions	3 Months Ended
	Mar. 31, 2026 USD ($)
Debt Instrument [Line Items]
Total Issuances	$ 2,932
Other Long-term Debt | Transource Energy
Debt Instrument [Line Items]
Total Issuances	18
Other Long-term Debt | AEP TRANSMISSION COMPANY, LLC
Debt Instrument [Line Items]
Total Issuances	114
Senior Unsecured Notes | AEP TEXAS INC. | 5.20% Senior Unsecured Notes
Debt Instrument [Line Items]
Total Issuances	$ 750
Interest Rate	5.20%
Senior Unsecured Notes | INDIANA MICHIGAN POWER COMPANY | 5.60% Senior Unsecured Notes
Debt Instrument [Line Items]
Total Issuances	$ 650
Interest Rate	5.60%
Senior Unsecured Notes | SOUTHWESTERN ELECTRIC POWER COMPANY | 5.20% Senior Unsecured Notes
Debt Instrument [Line Items]
Total Issuances	$ 600
Interest Rate	5.20%
Senior Unsecured Notes | SOUTHWESTERN ELECTRIC POWER COMPANY | 5.30% Senior Unsecured Notes
Debt Instrument [Line Items]
Total Issuances	$ 300
Interest Rate	5.30%
Senior Unsecured Notes | SOUTHWESTERN ELECTRIC POWER COMPANY | 5.90% Senior Unsecured Notes
Debt Instrument [Line Items]
Total Issuances	$ 500
Interest Rate	5.90%