v3.26.3
FAIR VALUE MEASUREMENTS - Significant Unobservable Inputs (Details) - USD ($)
Sep. 30, 2026
Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets $ 854,000,000 $ 617,000,000
Fair value, liabilities 423,000,000 310,000,000
APCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 188,000,000 82,000,000
Fair value, liabilities 18,000,000 3,000,000
I&M    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 26,000,000 10,000,000
Fair value, liabilities 1,000,000 0
OPCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 0 0
Fair value, liabilities 22,000,000 33,000,000
PSO    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 41,000,000 42,000,000
Fair value, liabilities 34,000,000 28,000,000
SWEPCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 43,000,000 35,000,000
Fair value, liabilities 12,000,000 11,000,000
Energy Contracts | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 230,000,000 224,000,000
Fair value, liabilities 181,000,000 144,000,000
Energy Contracts | Level 3 | OPCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 0 0
Fair value, liabilities $ 22,000,000 $ 33,000,000
Energy Contracts | Level 3 | Low | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 0.70 5.65
Input/Range, liability 0.70 5.65
Energy Contracts | Level 3 | Low | OPCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 13.09 21.44
Input/Range, liability 13.09 21.44
Energy Contracts | Level 3 | High | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 235.15 141.75
Input/Range, liability 235.15 141.75
Energy Contracts | Level 3 | High | OPCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 150.37 85.92
Input/Range, liability 150.37 85.92
Energy Contracts | Level 3 | Weighted Average | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 56.21 50.61
Input/Range, liability 56.21 50.61
Energy Contracts | Level 3 | Weighted Average | OPCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 55.59 50.10
Input/Range, liability 55.59 50.10
FTRs | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets $ 345,000,000 $ 187,000,000
Fair value, liabilities 21,000,000 8,000,000
FTRs | Level 3 | APCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 183,000,000 81,000,000
Fair value, liabilities 0 0
FTRs | Level 3 | I&M    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 28,000,000 9,000,000
Fair value, liabilities 5,000,000 0
FTRs | Level 3 | PSO    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 41,000,000 43,000,000
Fair value, liabilities 0 2,000,000
FTRs | Level 3 | SWEPCo    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value, assets 43,000,000 37,000,000
Fair value, liabilities $ 0 $ 2,000,000
FTRs | Level 3 | Low | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset (78.84) (32.49)
Input/Range, liability (78.84) (32.49)
FTRs | Level 3 | Low | APCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset (2.15) (0.26)
Input/Range, liability (2.15) (0.26)
FTRs | Level 3 | Low | I&M | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset (8.24) (0.46)
Input/Range, liability (8.24) (0.46)
FTRs | Level 3 | Low | PSO | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset (20.83) (32.49)
Input/Range, liability (20.83) (32.49)
FTRs | Level 3 | Low | SWEPCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset (20.83) (32.49)
Input/Range, liability (20.83) (32.49)
FTRs | Level 3 | High | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 104.78 21.68
Input/Range, liability 104.78 21.68
FTRs | Level 3 | High | APCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 35.03 17.55
Input/Range, liability 35.03 17.55
FTRs | Level 3 | High | I&M | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 35.03 21.68
Input/Range, liability 35.03 21.68
FTRs | Level 3 | High | PSO | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 6.06 8.54
Input/Range, liability 6.06 8.54
FTRs | Level 3 | High | SWEPCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 6.06 8.54
Input/Range, liability 6.06 8.54
FTRs | Level 3 | Weighted Average | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 2.08 0.49
Input/Range, liability 2.08 0.49
FTRs | Level 3 | Weighted Average | APCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 5.51 3.47
Input/Range, liability 5.51 3.47
FTRs | Level 3 | Weighted Average | I&M | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset 1.44 1.60
Input/Range, liability 1.44 1.60
FTRs | Level 3 | Weighted Average | PSO | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset (7.01) (5.49)
Input/Range, liability (7.01) (5.49)
FTRs | Level 3 | Weighted Average | SWEPCo | Forward Market Price    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Input/Range, asset (7.01) (5.49)
Input/Range, liability (7.01) (5.49)