v3.26.3
RATE MATTERS - Regulatory Assets Pending Final Approval (Details) - USD ($)
$ in Millions
Sep. 30, 2026
May 31, 2026
Mar. 31, 2026
Dec. 31, 2025
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets $ 4,967     $ 4,804
AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 470     402
AEP TRANSMISSION COMPANY, LLC        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 87     73
APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 1,378     1,439
INDIANA MICHIGAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 582     585
PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 683     637
SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 913     903
Virginia | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
Regulatory asset, requested to be financed through securitization   $ 1,400    
Total Regulatory Assets Pending Final Regulatory Approval        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 1,534     1,307
Total Regulatory Assets Pending Final Regulatory Approval | AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 264     181
Total Regulatory Assets Pending Final Regulatory Approval | AEP TRANSMISSION COMPANY, LLC        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 9     9
Total Regulatory Assets Pending Final Regulatory Approval | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 396     440
Total Regulatory Assets Pending Final Regulatory Approval | INDIANA MICHIGAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 153     118
Total Regulatory Assets Pending Final Regulatory Approval | PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 123     84
Total Regulatory Assets Pending Final Regulatory Approval | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 517     445
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 264     220
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 264     220
UTM Deferred Costs | Regulatory Assets Currently Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 89     56
UTM Deferred Costs | Regulatory Assets Currently Earning a Return | AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 89     56
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 73     17
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return | AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 34     17
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 39     1
Plant Retirement Costs - Unrecovered Plant, Pirkey - Texas, FERC | Regulatory Assets Currently Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 61     93
Plant Retirement Costs - Unrecovered Plant, Pirkey - Texas, FERC | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 61     93
Storm-Related Costs | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
Regulatory asset, requested to be financed through securitization, approved   141    
Storm-Related Costs | Virginia | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
Regulatory asset, requested to be financed through securitization   $ 141    
Storm-Related Costs | Regulatory Assets Currently Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 46     43
Storm-Related Costs | Regulatory Assets Currently Earning a Return | AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 41     41
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 376     363
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 51     31
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | INDIANA MICHIGAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 57     29
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 38     25
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 59     43
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia        
Regulatory Asset [Line Items]        
Regulatory asset, requested to be financed through securitization     $ 40  
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 70     39
Regulatory asset, requested to be financed through securitization     $ 40  
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | Virginia | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 69     172
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 7     6
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 2     2
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | INDIANA MICHIGAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 5     4
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 5     2
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 169     136
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 9     9
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 35     18
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | INDIANA MICHIGAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 9     7
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 1     8
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 17     20
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 289     257
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 188     169
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | INDIANA MICHIGAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 82     78
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 12     6
NOLC Costs | Regulatory Assets Currently Not Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 83     89
NOLC Costs | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 17     23
NOLC Costs | Regulatory Assets Currently Not Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 65     66
Deferred Pension and OPEB Costs | Regulatory Assets Currently Not Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 40     27
Deferred Pension and OPEB Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 40     27
Vegetation Management Costs | Regulatory Assets Currently Not Earning a Return        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 37     0
Vegetation Management Costs | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 17     0
Income Taxes, Net | Regulatory Assets Currently Earning a Return | AEP TRANSMISSION COMPANY, LLC        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 9     9
Income Taxes, Net | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 7     0
Pension Settlement | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 15     16
Virginia Corporate Alternative Minimum Tax | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 0     13
West Virginia Corporate Alternative Minimum Tax | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 0     11
Oklahoma Senate Bill 998 Deferral | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets 28     9
Generation PBA and Delayed Retirement Deferral | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA        
Regulatory Asset [Line Items]        
 Noncurrent Regulatory Assets $ 27     $ 13