FINANCING ACTIVITIES - Long-term Debt Subsequent Events Narrative (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
	Feb. 12, 2026	Jan. 31, 2026	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Debt retired			$ 3,649	$ 2,685	$ 2,196
AEP TRANSMISSION COMPANY, LLC
Debt Instrument [Line Items]
Debt retired			102	95	60
AEP TRANSMISSION COMPANY, LLC | Other Long-term Debt | Subsequent Event
Debt Instrument [Line Items]
Total issuances		$ 114
I&M
Debt Instrument [Line Items]
Debt retired			300	103	343
I&M | Notes Payable - Nonaffiliated | Subsequent Event
Debt Instrument [Line Items]
Debt retired		11
APCo
Debt Instrument [Line Items]
Debt retired			548	414	27
APCo | Subsequent Event
Debt Instrument [Line Items]
Proceeds from contributed capital	$ 81
APCo | Securitization Bonds | Subsequent Event
Debt Instrument [Line Items]
Debt retired	14
OHIO POWER COMPANY | Subsequent Event
Debt Instrument [Line Items]
Proceeds from contributed capital	38
SOUTHWESTERN ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Debt retired			11	0	94
SOUTHWESTERN ELECTRIC POWER COMPANY | Subsequent Event
Debt Instrument [Line Items]
Proceeds from contributed capital	128
AEP Texas
Debt Instrument [Line Items]
Debt retired			$ 724	$ 296	$ 279
AEP Texas | Securitization Bonds | Subsequent Event
Debt Instrument [Line Items]
Debt retired	$ 12
Transource Energy | Other Long-term Debt | Subsequent Event
Debt Instrument [Line Items]
Total issuances		$ 14