LEASES - Lease Rental Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Lessee, Lease, Description [Line Items]
Operating Lease Cost	$ 137	$ 146	$ 150
Finance Lease Cost:
Amortization of Right-of-Use Assets	51	64	69
Interest on Lease Liabilities	10	12	12
Total Lease Rental Costs	198	222	231
AEP TEXAS INC.
Lessee, Lease, Description [Line Items]
Operating Lease Cost	18	32	34
Finance Lease Cost:
Amortization of Right-of-Use Assets	8	8	8
Interest on Lease Liabilities	2	1	1
Total Lease Rental Costs	28	41	43
AEPTCo
Lessee, Lease, Description [Line Items]
Operating Lease Cost	1	1	1
Finance Lease Cost:
Amortization of Right-of-Use Assets	0	0	0
Interest on Lease Liabilities	0	0	0
Total Lease Rental Costs	1	1	1
APCo
Lessee, Lease, Description [Line Items]
Operating Lease Cost	20	18	19
Finance Lease Cost:
Amortization of Right-of-Use Assets	9	9	8
Interest on Lease Liabilities	1	2	2
Total Lease Rental Costs	30	29	29
I&M
Lessee, Lease, Description [Line Items]
Operating Lease Cost	20	20	20
Finance Lease Cost:
Amortization of Right-of-Use Assets	6	7	7
Interest on Lease Liabilities	2	2	2
Total Lease Rental Costs	28	29	29
OPCo
Lessee, Lease, Description [Line Items]
Operating Lease Cost	17	17	17
Finance Lease Cost:
Amortization of Right-of-Use Assets	4	5	5
Interest on Lease Liabilities	1	1	1
Total Lease Rental Costs	22	23	23
PSO
Lessee, Lease, Description [Line Items]
Operating Lease Cost	14	14	14
Finance Lease Cost:
Amortization of Right-of-Use Assets	3	3	3
Interest on Lease Liabilities	1	1	1
Total Lease Rental Costs	18	18	18
SWEPCo
Lessee, Lease, Description [Line Items]
Operating Lease Cost	20	18	18
Finance Lease Cost:
Amortization of Right-of-Use Assets	4	13	20
Interest on Lease Liabilities	1	1	1
Total Lease Rental Costs	$ 25	$ 32	$ 39