DERIVATIVES AND HEDGING - Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Commodity
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	$ 63	$ 78
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	35	31
Commodity | AEP Texas
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	0	0
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Commodity | APCo
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	0	0
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Commodity | I&M
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	0	0
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Commodity | PSO
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	0	0
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Commodity | SWEPCo
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	0	0
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Interest Rate
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	(1)	(1)
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Interest Rate | AEP Texas
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	6	6
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	1	1
Interest Rate | APCo
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	4	4
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	1	1
Interest Rate | I&M
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	(5)	(5)
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Interest Rate | PSO
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	2	2
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	0	0
Interest Rate | SWEPCo
Derivative Instruments and Hedging Activities Disclosures [Line Items]
AOCI Gain (Loss) Net of Tax	1	1
Portion Expected to be Reclassed to Net Income During the Next Twelve Months	$ 0	$ 0