VARIABLE INTEREST ENTITIES AND EQUITY METHOD INVESTMENTS - Investments (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outstanding indebtedness	$ 873	$ 997
Capital Contribution From Parent
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	5	5
Maximum Exposure	5	5
Total Investment
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	5	5
Maximum Exposure	384	438
AEP's Ratio of OVEC Debt
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	0	0
Maximum Exposure	379	433
AEP Texas | Billings from AEP Service Corporation
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	51	26
Maximum Exposure	51	26
AEPTCo | Billings from AEP Service Corporation
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	54	29
Maximum Exposure	54	29
APCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outstanding indebtedness	137	156
APCo | Billings from AEP Service Corporation
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	52	36
Maximum Exposure	52	36
I&M
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outstanding indebtedness	68	78
I&M | Billings from AEP Service Corporation
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	32	25
Maximum Exposure	32	25
OPCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outstanding indebtedness	174	199
OPCo | Billings from AEP Service Corporation
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	47	35
Maximum Exposure	47	35
PSO | Billings from AEP Service Corporation
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	29	19
Maximum Exposure	29	19
SWEPCo | Billings from AEP Service Corporation
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	32	22
Maximum Exposure	32	22
SWEPCo | Capital Contribution From Parent
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	7	7
Maximum Exposure	7	7
SWEPCo | Retained Earnings
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	1	1
Maximum Exposure	1	1
SWEPCo | SWEPCo's Share of Obligations
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	0	0
Maximum Exposure	11	16
SWEPCo | Total Investment
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet	8	8
Maximum Exposure	$ 19	$ 24