DERIVATIVES AND HEDGING - Schedule of Gain (Loss) Recognized on Risk Management Contracts (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	$ 253	$ (40)
Regulatory Assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	(6)	53
Regulatory Liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	181	80
AEP TEXAS INC.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	2	0
AEP TEXAS INC. | Regulatory Assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
AEP TEXAS INC. | Regulatory Liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	2	0
APPALACHIAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	109	42
APPALACHIAN POWER COMPANY | Regulatory Assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	(3)	0
APPALACHIAN POWER COMPANY | Regulatory Liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	103	39
INDIANA MICHIGAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	(24)	(28)
INDIANA MICHIGAN POWER COMPANY | Regulatory Assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
INDIANA MICHIGAN POWER COMPANY | Regulatory Liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	7	5
OHIO POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	5	51
OHIO POWER COMPANY | Regulatory Assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	2	48
OHIO POWER COMPANY | Regulatory Liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	3	3
PUBLIC SERVICE COMPANY OF OKLAHOMA
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	32	16
PUBLIC SERVICE COMPANY OF OKLAHOMA | Regulatory Assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	(3)	4
PUBLIC SERVICE COMPANY OF OKLAHOMA | Regulatory Liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	35	12
SOUTHWESTERN ELECTRIC POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	7	15
SOUTHWESTERN ELECTRIC POWER COMPANY | Regulatory Assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	(3)	1
SOUTHWESTERN ELECTRIC POWER COMPANY | Regulatory Liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	10	14
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	9	3
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation | AEP TEXAS INC.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation | APPALACHIAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	9	3
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation | INDIANA MICHIGAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation | OHIO POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation | PUBLIC SERVICE COMPANY OF OKLAHOMA
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation | SOUTHWESTERN ELECTRIC POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Vertically Integrated Utilities | Revenues
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	(30)	(33)
Vertically Integrated Utilities | Revenues | AEP TEXAS INC.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Vertically Integrated Utilities | Revenues | APPALACHIAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Vertically Integrated Utilities | Revenues | INDIANA MICHIGAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Vertically Integrated Utilities | Revenues | OHIO POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Vertically Integrated Utilities | Revenues | PUBLIC SERVICE COMPANY OF OKLAHOMA
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Vertically Integrated Utilities | Revenues | SOUTHWESTERN ELECTRIC POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Generation & Marketing | Revenues
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	99	(143)
Generation & Marketing | Revenues | AEP TEXAS INC.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Generation & Marketing | Revenues | APPALACHIAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Generation & Marketing | Revenues | INDIANA MICHIGAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Generation & Marketing | Revenues | OHIO POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Generation & Marketing | Revenues | PUBLIC SERVICE COMPANY OF OKLAHOMA
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Generation & Marketing | Revenues | SOUTHWESTERN ELECTRIC POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Electric Generation, Transmission and Distribution | Revenues
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Electric Generation, Transmission and Distribution | Revenues | AEP TEXAS INC.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Electric Generation, Transmission and Distribution | Revenues | APPALACHIAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Electric Generation, Transmission and Distribution | Revenues | INDIANA MICHIGAN POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	(31)	(33)
Electric Generation, Transmission and Distribution | Revenues | OHIO POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Electric Generation, Transmission and Distribution | Revenues | PUBLIC SERVICE COMPANY OF OKLAHOMA
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	0	0
Electric Generation, Transmission and Distribution | Revenues | SOUTHWESTERN ELECTRIC POWER COMPANY
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total Gain (Loss) on Risk Management Contracts	$ 0	$ 0