EFFECTS OF REGULATION - Regulatory Assets - AEPTCO (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 4,804	$ 5,129
Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	1,307	1,311
Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	3,497	3,818
Earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	435	395
Earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	1,341	1,711
Earns/earning a return | Approved for recovery | PJM/SPP Annual Formula Rate True-up
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 35	0
Remaining Recovery Period	2 years
Does not earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 872	916
Does not earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	2,156	2,107
AEP TRANSMISSION COMPANY, LLC
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	73	0
AEP TRANSMISSION COMPANY, LLC | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	64	0
AEP TRANSMISSION COMPANY, LLC | Earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	9	0
AEP TRANSMISSION COMPANY, LLC | Earns/earning a return | Pending final regulatory approval | Income Taxes, Net
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	9	0
AEP TRANSMISSION COMPANY, LLC | Earns/earning a return | Approved for recovery | Income Taxes, Net
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	49	0
AEP TRANSMISSION COMPANY, LLC | Earns/earning a return | Approved for recovery | PJM/SPP Annual Formula Rate True-up
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 15	$ 0
Remaining Recovery Period	2 years
AEP TRANSMISSION COMPANY, LLC | Does not earns/earning a return | Approved for recovery | Excess ADIT that is Not Subject to Rate Normalization Requirements
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 6
Remaining Recovery Period	2 years