VARIABLE INTEREST ENTITIES AND EQUITY METHOD INVESTMENTS - Billings (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
AEP Texas
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE	$ 278	$ 243	$ 229
AEPTCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE	319	290	270
APCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE	352	335	325
I&M
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE	189	188	178
OPCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE	282	283	270
PSO
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE	176	157	139
SWEPCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE	$ 207	$ 194	$ 185