DERIVATIVES AND HEDGING - Schedule of Notional Volume of Derivative Instruments (Details) gal in Millions, MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2026 USD ($) MMBTU MWh gal	Dec. 31, 2025 USD ($) MWh MMBTU gal
Power (MWhs)
Derivative [Line Items]
Notional amount, energy measure | MWh	292	327
Power (MWhs) | AEP TEXAS INC.
Derivative [Line Items]
Notional amount, energy measure | MWh	0	0
Power (MWhs) | APCo
Derivative [Line Items]
Notional amount, energy measure | MWh	9	23
Power (MWhs) | I&M
Derivative [Line Items]
Notional amount, energy measure | MWh	4	8
Power (MWhs) | OPCo
Derivative [Line Items]
Notional amount, energy measure | MWh	2	2
Power (MWhs) | PSO
Derivative [Line Items]
Notional amount, energy measure | MWh	3	8
Power (MWhs) | SWEPCo
Derivative [Line Items]
Notional amount, energy measure | MWh	2	6
Natural Gas (MMBtus)
Derivative [Line Items]
Notional amount, energy measure | MMBTU	190	166
Natural Gas (MMBtus) | AEP TEXAS INC.
Derivative [Line Items]
Notional amount, energy measure | MMBTU	0	0
Natural Gas (MMBtus) | APCo
Derivative [Line Items]
Notional amount, energy measure | MMBTU	46	48
Natural Gas (MMBtus) | I&M
Derivative [Line Items]
Notional amount, energy measure | MMBTU	0	0
Natural Gas (MMBtus) | OPCo
Derivative [Line Items]
Notional amount, energy measure | MMBTU	0	0
Natural Gas (MMBtus) | PSO
Derivative [Line Items]
Notional amount, energy measure | MMBTU	50	44
Natural Gas (MMBtus) | SWEPCo
Derivative [Line Items]
Notional amount, energy measure | MMBTU	26	26
Heating Oil and Gasoline (Gallons)
Derivative [Line Items]
Notional amount, volume | gal	9	8
Heating Oil and Gasoline (Gallons) | AEP TEXAS INC.
Derivative [Line Items]
Notional amount, volume | gal	2	2
Heating Oil and Gasoline (Gallons) | APCo
Derivative [Line Items]
Notional amount, volume | gal	1	1
Heating Oil and Gasoline (Gallons) | I&M
Derivative [Line Items]
Notional amount, volume | gal	2	2
Heating Oil and Gasoline (Gallons) | OPCo
Derivative [Line Items]
Notional amount, volume | gal	1	1
Heating Oil and Gasoline (Gallons) | PSO
Derivative [Line Items]
Notional amount, volume | gal	1	1
Heating Oil and Gasoline (Gallons) | SWEPCo
Derivative [Line Items]
Notional amount, volume | gal	1	1
Interest Rate (USD)
Derivative [Line Items]
Notional amount	$ 30	$ 40
Interest Rate (USD) | AEP TEXAS INC.
Derivative [Line Items]
Notional amount	0	0
Interest Rate (USD) | APCo
Derivative [Line Items]
Notional amount	0	0
Interest Rate (USD) | I&M
Derivative [Line Items]
Notional amount	0	0
Interest Rate (USD) | OPCo
Derivative [Line Items]
Notional amount	0	0
Interest Rate (USD) | PSO
Derivative [Line Items]
Notional amount	0	0
Interest Rate (USD) | SWEPCo
Derivative [Line Items]
Notional amount	0	0
Interest Rate
Derivative [Line Items]
Notional amount	500	500
Interest Rate | AEP TEXAS INC.
Derivative [Line Items]
Notional amount	0	0
Interest Rate | APCo
Derivative [Line Items]
Notional amount	0	0
Interest Rate | I&M
Derivative [Line Items]
Notional amount	0	0
Interest Rate | OPCo
Derivative [Line Items]
Notional amount	0	0
Interest Rate | PSO
Derivative [Line Items]
Notional amount	0	0
Interest Rate | SWEPCo
Derivative [Line Items]
Notional amount	$ 0	$ 0