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RATE MATTERS - Regulatory Assets Pending Final Approval (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets $ 4,950.2   $ 5,129.2
Regulatory assets, current 380.6   445.9
AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 396.3   353.6
APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 1,498.9   1,366.0
Regulatory assets, current 79.3   148.1
Regulatory asset, requested to be financed through securitization 2,527.6    
I&M      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 620.4   548.1
Regulatory assets, current 0.0   10.6
OPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 347.6   379.1
PSO      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 603.5   527.8
Regulatory assets, current 22.3   64.7
SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 922.2   921.3
Regulatory assets, current 106.7   106.6
West Virginia | APCo      
Regulatory Asset [Line Items]      
Regulatory asset, requested to be financed through securitization   $ 2,400.0  
Total Regulatory Assets Pending Final Regulatory Approval      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 1,492.5   1,348.0
Total Regulatory Assets Pending Final Regulatory Approval | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 156.9   77.1
Total Regulatory Assets Pending Final Regulatory Approval | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 572.6   535.5
Total Regulatory Assets Pending Final Regulatory Approval | I&M      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 111.7   115.0
Total Regulatory Assets Pending Final Regulatory Approval | OPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 0.9   0.5
Total Regulatory Assets Pending Final Regulatory Approval | PSO      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 70.7   30.3
Total Regulatory Assets Pending Final Regulatory Approval | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 551.3   491.4
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 206.2   168.6
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 206.2   168.6
Pirkey Plant Accelerated Depreciation | Regulatory Assets Currently Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 134.1   121.3
Pirkey Plant Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 134.1   121.3
Storm-Related Costs | APCo      
Regulatory Asset [Line Items]      
Regulatory asset, requested to be financed through securitization 157.9    
Storm-Related Costs | West Virginia | APCo      
Regulatory Asset [Line Items]      
Regulatory asset, requested to be financed through securitization   $ 118.0  
Storm-Related Costs | Regulatory Assets Currently Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 53.5   51.0
Storm-Related Costs | Regulatory Assets Currently Earning a Return | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 41.3   41.3
Storm-Related Costs | Regulatory Assets Currently Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 12.2   9.7
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 202.2   300.8
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 34.4   13.1
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 49.6   144.2
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | I&M      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 29.3   6.3
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | PSO      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 22.4   4.9
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 44.9   39.9
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia      
Regulatory Asset [Line Items]      
Regulatory asset, requested to be financed through securitization 40.0    
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia | APCo      
Regulatory Asset [Line Items]      
Regulatory asset, requested to be financed through securitization 40.0    
Unrecovered Winter Storm Fuel Costs | Regulatory Assets Currently Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 47.2   70.7
Unrecovered Winter Storm Fuel Costs | Regulatory Assets Currently Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 47.2   70.7
Regulatory assets, current 37.0   37.0
Unified Tracking Mechanism Deferred Costs | Regulatory Assets Currently Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 39.2   0.0
Unified Tracking Mechanism Deferred Costs | Regulatory Assets Currently Earning a Return | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 39.2   0.0
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 8.6   0.0
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 30.9   20.7
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 1.5   1.1
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | I&M      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 3.3   6.4
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | OPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 0.9   0.4
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 4.3   1.1
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 130.8   86.3
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 2.9   1.3
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 20.7   11.9
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | I&M      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 1.7   1.6
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | OPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 0.0   0.1
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | PSO      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 7.8   1.2
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 19.5   18.7
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 386.5   357.4
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 305.8   282.1
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | I&M      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 77.4   74.0
2024-2025 Virginia Biennial Under-Earnings | Regulatory Assets Currently Not Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 166.0   78.4
2024-2025 Virginia Biennial Under-Earnings | Regulatory Assets Currently Not Earning a Return | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 166.0   78.4
NOLC Costs | Regulatory Assets Currently Not Earning a Return      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 95.9   92.8
NOLC Costs | Regulatory Assets Currently Not Earning a Return | I&M      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 0.0   26.7
NOLC Costs | Regulatory Assets Currently Not Earning a Return | PSO      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 25.4   16.4
NOLC Costs | Regulatory Assets Currently Not Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 70.5   49.6
Deferred Pension and OPEB Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 24.7   15.6
Line Inspection Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 5.8   5.8
Pension Settlement | Regulatory Assets Currently Not Earning a Return | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 16.7   17.8
Pension Settlement | Regulatory Assets Currently Not Earning a Return | PSO      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 7.4   7.8
Virginia Retail Consumables Deferral | Regulatory Assets Currently Not Earning a Return | APCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 12.3   0.0
Generation PBA and Delayed Retirement Deferral | Regulatory Assets Currently Not Earning a Return | PSO      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets 7.7   0.0
Dolet Hills Power Station Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SWEPCo      
Regulatory Asset [Line Items]      
 Noncurrent Regulatory Assets $ 12.4   $ 11.8