DERIVATIVES AND HEDGING - Schedule of Notional Volume of Derivative Instruments (Details) gal in Millions, MWh in Millions, MMBTU in Millions, $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2026 USD ($) MMBTU MWh gal	Dec. 31, 2025 USD ($) MWh MMBTU gal
Power (MWhs)
Derivative [Line Items]
Notional amount, energy measure \| MWh	336	327
Power (MWhs) \| AEP Texas
Derivative [Line Items]
Notional amount, energy measure \| MWh	0	0
Power (MWhs) \| APCo
Derivative [Line Items]
Notional amount, energy measure \| MWh	34	23
Power (MWhs) \| I&M
Derivative [Line Items]
Notional amount, energy measure \| MWh	18	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	6	8
Power (MWhs) \| SWEPCo
Derivative [Line Items]
Notional amount, energy measure \| MWh	6	6
Natural Gas (MMBtus)
Derivative [Line Items]
Notional amount, energy measure \| MMBTU	204	166
Natural Gas (MMBtus) \| AEP Texas
Derivative [Line Items]
Notional amount, energy measure \| MMBTU	0	0
Natural Gas (MMBtus) \| APCo
Derivative [Line Items]
Notional amount, energy measure \| MMBTU	43	48
Natural Gas (MMBtus) \| I&M
Derivative [Line Items]
Notional amount, energy measure \| MMBTU	5	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	72	44
Natural Gas (MMBtus) \| SWEPCo
Derivative [Line Items]
Notional amount, energy measure \| MMBTU	18	26
Heating Oil and Gasoline (Gallons)
Derivative [Line Items]
Notional amount, volume \| gal	12	8
Heating Oil and Gasoline (Gallons) \| AEP Texas
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	4	2
Heating Oil and Gasoline (Gallons) \| OPCo
Derivative [Line Items]
Notional amount, volume \| gal	2	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	$ 38	$ 40
Interest Rate (USD) \| AEP Texas
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
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

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-5A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
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-Paragraph 18
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-Publisher FASB
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
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- Definition

Nominal energy measure used to calculate payments on a derivative instrument.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
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-URI https://asc.fasb.org/1943274/2147480434/815-10-50-5

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

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-Topic 815
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-Section 55
-Paragraph 181
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Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-181

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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