LEASES - Supplemental Lease Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Weighted-Average Remaining Lease Term (years):
Operating Leases	17 years 3 months 29 days	12 years 9 months 18 days
Finance Leases	4 years 6 months 10 days	4 years 9 months 21 days
Weighted-Average Discount Rate:
Operating Leases	4.74%	3.89%
Finance Leases	6.36%	6.43%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 135	$ 144
Operating Cash Flows Used for Finance Leases	10	12
Financing Cash Flows Used for Finance Leases	51	65	$ 68
Non-cash Acquisitions Under Operating Leases	$ 190	$ 82
AEP TEXAS INC.
Weighted-Average Remaining Lease Term (years):
Operating Leases	4 years 3 months 29 days	4 years 5 months 12 days
Finance Leases	4 years 9 months 18 days	5 years 14 days
Weighted-Average Discount Rate:
Operating Leases	4.57%	4.29%
Finance Leases	5.99%	5.73%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 18	$ 32
Operating Cash Flows Used for Finance Leases	1	1
Financing Cash Flows Used for Finance Leases	8	8	7
Non-cash Acquisitions Under Operating Leases	$ 12	$ 6
AEPTCo
Weighted-Average Remaining Lease Term (years):
Operating Leases	3 years 3 months 14 days	2 years 3 months 14 days
Finance Leases	0 years	0 years
Weighted-Average Discount Rate:
Operating Leases	4.51%	4.55%
Finance Leases	0.00%	0.00%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 1	$ 1
Operating Cash Flows Used for Finance Leases	0	0
Financing Cash Flows Used for Finance Leases	0	0
Non-cash Acquisitions Under Operating Leases	$ 1	$ 1
APCo
Weighted-Average Remaining Lease Term (years):
Operating Leases	13 years 10 days	5 years 4 months 20 days
Finance Leases	4 years 5 months 1 day	4 years 1 month 2 days
Weighted-Average Discount Rate:
Operating Leases	5.08%	4.20%
Finance Leases	5.73%	6.69%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 20	$ 18
Operating Cash Flows Used for Finance Leases	1	2
Financing Cash Flows Used for Finance Leases	9	9	8
Non-cash Acquisitions Under Operating Leases	$ 44	$ 9
I&M
Weighted-Average Remaining Lease Term (years):
Operating Leases	3 years 8 months 23 days	4 years 5 months 4 days
Finance Leases	5 years 1 month 13 days	4 years 9 months 29 days
Weighted-Average Discount Rate:
Operating Leases	4.61%	4.11%
Finance Leases	9.04%	9.07%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 20	$ 20
Operating Cash Flows Used for Finance Leases	2	2
Financing Cash Flows Used for Finance Leases	6	7	7
Non-cash Acquisitions Under Operating Leases	$ 17	$ 15
OPCo
Weighted-Average Remaining Lease Term (years):
Operating Leases	4 years 14 days	4 years 7 months 20 days
Finance Leases	4 years 2 months 26 days	4 years 6 months 29 days
Weighted-Average Discount Rate:
Operating Leases	4.36%	4.17%
Finance Leases	5.74%	5.59%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 17	$ 17
Operating Cash Flows Used for Finance Leases	1	1
Financing Cash Flows Used for Finance Leases	4	5	5
Non-cash Acquisitions Under Operating Leases	$ 4	$ 5
PSO
Weighted-Average Remaining Lease Term (years):
Operating Leases	25 years 7 months 2 days	23 years 8 months 4 days
Finance Leases	4 years 7 months 9 days	5 years 5 months 8 days
Weighted-Average Discount Rate:
Operating Leases	4.48%	3.76%
Finance Leases	5.71%	5.48%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 13	$ 13
Operating Cash Flows Used for Finance Leases	1	1
Financing Cash Flows Used for Finance Leases	3	3	3
Non-cash Acquisitions Under Operating Leases	$ 28	$ 3
SWEPCo
Weighted-Average Remaining Lease Term (years):
Operating Leases	29 years 7 days	21 years 11 months 19 days
Finance Leases	5 years 7 months 6 days	6 years 1 month 20 days
Weighted-Average Discount Rate:
Operating Leases	4.96%	3.60%
Finance Leases	5.90%	5.73%
Cash paid for amounts included in the measurement of lease liabilities:
Operating Cash Flows Used for Operating Leases	$ 20	$ 17
Operating Cash Flows Used for Finance Leases	1	2
Financing Cash Flows Used for Finance Leases	4	14	$ 19
Non-cash Acquisitions Under Operating Leases	$ 70	$ 27