RELATED PARTY TRANSACTIONS - Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	$ 21,702	$ 19,970	$ 19,456
AEP Texas
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	2,194	2,081	1,906
AEP Texas | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	5	5	5
AEPTCo
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	2,249	1,951	1,720
AEPTCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	1,869	1,512	1,317
APCo
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	4,183	4,039	3,740
APCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	279	248	239
I&M
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	3,051	2,604	2,522
I&M | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	69	66	57
OPCo
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	3,880	3,781	3,803
OPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	45	23	31
PSO
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	2,019	1,849	1,977
PSO | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	9	7	1
SWEPCo
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	2,336	2,043	2,192
SWEPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	83	62	47
Direct Sales to East Affiliates | AEP Texas | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Direct Sales to East Affiliates | AEPTCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Direct Sales to East Affiliates | APCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	165	159	159
Direct Sales to East Affiliates | I&M | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Direct Sales to East Affiliates | OPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Direct Sales to East Affiliates | PSO | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Direct Sales to East Affiliates | SWEPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Direct Sales to West Affiliates | AEP Texas | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0
Direct Sales to West Affiliates | AEPTCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0
Direct Sales to West Affiliates | APCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0
Direct Sales to West Affiliates | I&M | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0
Direct Sales to West Affiliates | OPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0
Direct Sales to West Affiliates | PSO | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	4
Direct Sales to West Affiliates | SWEPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0
Transmission Revenues | AEP Texas | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Transmission Revenues | AEPTCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	1,848	1,491	1,304
Transmission Revenues | APCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	99	79	71
Transmission Revenues | I&M | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	(1)	(9)	(11)
Transmission Revenues | OPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	13	(7)	3
Transmission Revenues | PSO | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	0	0	0
Transmission Revenues | SWEPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	81	61	45
Barging, Urea Transloading and Other Transportation Services | AEP Texas | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers			0
Barging, Urea Transloading and Other Transportation Services | AEPTCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers			0
Barging, Urea Transloading and Other Transportation Services | APCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers			0
Barging, Urea Transloading and Other Transportation Services | I&M | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers			59
Barging, Urea Transloading and Other Transportation Services | OPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers			0
Barging, Urea Transloading and Other Transportation Services | PSO | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers			0
Barging, Urea Transloading and Other Transportation Services | SWEPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers			0
Other Revenues | AEP Texas | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	5	5	5
Other Revenues | AEPTCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	21	21	13
Other Revenues | APCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	15	10	9
Other Revenues | I&M | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	70	75	9
Other Revenues | OPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	32	30	28
Other Revenues | PSO | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	5	7	1
Other Revenues | SWEPCo | Affiliated Entity
Related Party Transaction [Line Items]
Total Revenues from Contracts with Customers	$ 2	$ 1	$ 2