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FAIR VALUE MEASUREMENTS - Significant Unobservable Inputs (Details) - USD ($) | Jun. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | $ 728,200,000 | $ 499,500,000
Fair value, liabilities | 297,700,000 | 324,400,000
APCo |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 109,900,000 | 37,100,000
Fair value, liabilities | 2,300,000 | 2,200,000
I&M |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 12,300,000 | 18,400,000
Fair value, liabilities | 1,200,000 | 700,000
OPCo |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 0 | 0
Fair value, liabilities | 47,700,000 | 47,500,000
PSO |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 96,900,000 | 22,000,000.0
Fair value, liabilities | 8,100,000 | 5,800,000
SWEPCo |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 70,400,000 | 18,100,000
Fair value, liabilities | 3,800,000 | 2,300,000
Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 517,100,000 | 313,500,000
Fair value, liabilities | 134,300,000 | 147,900,000
Energy Contracts | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 204,200,000 | 221,200,000
Fair value, liabilities | 129,700,000 | 144,600,000
Energy Contracts | Level 3 | OPCo |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 0 | 0
Fair value, liabilities | $ 47,700,000 | $ 47,500,000
Energy Contracts | Level 3 | Low | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 4.80 | 2.75
Input/Range, liability | 4.80 | 2.75
Energy Contracts | Level 3 | Low | OPCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 12.54 | 14.53
Input/Range, liability | 12.54 | 14.53
Energy Contracts | Level 3 | High | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 129.40 | 149.30
Input/Range, liability | 129.40 | 149.30
Energy Contracts | Level 3 | High | OPCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 75.71 | 72.40
Input/Range, liability | 75.71 | 72.40
Energy Contracts | Level 3 | Weighted Average | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 47.56 | 49.34
Input/Range, liability | 47.56 | 49.34
Energy Contracts | Level 3 | Weighted Average | OPCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 41.08 | 42.44
Input/Range, liability | 41.08 | 42.44
FTRs | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | $ 312,900,000 | $ 92,300,000
Fair value, liabilities | 4,600,000 | 3,300,000
FTRs | Level 3 | APCo |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 108,600,000 | 35,200,000
Fair value, liabilities | 300,000 | 0
FTRs | Level 3 | I&M |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 13,000,000.0 | 6,900,000
Fair value, liabilities | 700,000 | 500,000
FTRs | Level 3 | PSO |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 97,000,000.0 | 20,800,000
Fair value, liabilities | 100,000 | 800,000
FTRs | Level 3 | SWEPCo |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair value, assets | 70,700,000 | 18,100,000
Fair value, liabilities | $ 1,600,000 | $ 600,000
FTRs | Level 3 | Low | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (32.49) | (29.48)
Input/Range, liability | (32.49) | (29.48)
FTRs | Level 3 | Low | APCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (1.40) | (0.25)
Input/Range, liability | (1.40) | (0.25)
FTRs | Level 3 | Low | I&M | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (0.90) | (4.07)
Input/Range, liability | (0.90) | (4.07)
FTRs | Level 3 | Low | PSO | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (32.49) | (29.48)
Input/Range, liability | (32.49) | (29.48)
FTRs | Level 3 | Low | SWEPCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (32.49) | (29.48)
Input/Range, liability | (32.49) | (29.48)
FTRs | Level 3 | High | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 28.81 | 19.70
Input/Range, liability | 28.81 | 19.70
FTRs | Level 3 | High | APCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 14.50 | 9.32
Input/Range, liability | 14.50 | 9.32
FTRs | Level 3 | High | I&M | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 14.50 | 9.32
Input/Range, liability | 14.50 | 9.32
FTRs | Level 3 | High | PSO | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 5.35 | 10.54
Input/Range, liability | 5.35 | 10.54
FTRs | Level 3 | High | SWEPCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 5.35 | 10.54
Input/Range, liability | 5.35 | 10.54
FTRs | Level 3 | Weighted Average | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (0.20) | 0.24
Input/Range, liability | (0.20) | 0.24
FTRs | Level 3 | Weighted Average | APCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 2.10 | 1.56
Input/Range, liability | 2.10 | 1.56
FTRs | Level 3 | Weighted Average | I&M | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | 1.05 | 1.34
Input/Range, liability | 1.05 | 1.34
FTRs | Level 3 | Weighted Average | PSO | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (5.18) | (3.88)
Input/Range, liability | (5.18) | (3.88)
FTRs | Level 3 | Weighted Average | SWEPCo | Forward Market Price |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Input/Range, asset | (5.18) | (3.88)
Input/Range, liability | (5.18) | (3.88)

X
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