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Commitments and Contingencies (Details) $ in Millions |  |  |  |  | 1 Months Ended | 9 Months Ended | 148 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Oct. 31, 2025 USD ($) | Jan. 01, 2024 USD ($) trust | Jan. 17, 2023 USD ($) | Jul. 03, 2018 | Jul. 31, 2025 USD ($) | Sep. 30, 2025 USD ($) trust timePeriod | Oct. 31, 2023 claim | Jul. 11, 2025 operator
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Production tax credit guarantees |  |  |  |  |  | $ 27.0 |  |
Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Settlement amount, awarded to company |  |  |  |  |  | $ 174.3 |  |
Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal | Subsequent Event |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Settlement amount, sought | $ 15.4 |  |  |  |  |  |  |
APS |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Maximum insurance against public liability per occurrence for a nuclear incident |  | $ 16,300.0 |  |  |  |  |  |
Maximum available nuclear liability insurance |  | 500.0 |  |  |  |  |  |
Remaining nuclear liability insurance through mandatory industry wide retrospective assessment program |  | 15,800.0 |  |  |  |  |  |
Maximum assessment per reactor for each nuclear incident |  | 165.9 |  |  |  |  |  |
Annual limit per incident with respect to maximum assessment |  | $ 24.7 |  |  |  |  |  |
Number of VIE lessor trusts | trust |  | 3 |  |  |  | 3 |  |
Maximum potential retrospective assessment per incident of APS |  | $ 144.9 |  |  |  |  |  |
Annual payment limitation with respect to maximum potential retrospective assessment |  | $ 21.6 |  |  |  |  |  |
Amount of "all risk" (including nuclear hazards) insurance for property damage to, and decontamination of, property at Palo Verde |  |  |  |  |  | $ 2,800.0 |  |
Request second-year energy price for exported energy |  |  |  |  |  | 24.2 |  |
Collateral assurance based on rating triggers |  |  |  |  |  | $ 66.4 |  |
Period to provide collateral assurance based on rating triggers |  |  |  |  |  | 20 days |  |
Number of power plant operators | operator |  |  |  |  |  |  |  | 25
Purchase commitment, amount |  |  |  |  | $ 7,300.0 |  |  |
Purchase commitment, period |  |  |  |  | 25 years |  |  |
APS | Surety Bonds Expiring in 2028 |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Surety bonds expiring, amount |  |  |  |  |  | $ 23.4 |  |
APS | Letter of Credit |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Outstanding letters of credit |  |  |  |  |  | 33.2 |  |
APS | Contaminated Groundwater Wells |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Costs related to investigation and study under Superfund site |  |  |  |  |  | 3.0 |  |
Remedial investigation work |  |  | $ 1.7 |  |  |  |  |
APS | Contaminated Groundwater Wells | Pending Litigation |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Settlement amount |  |  |  |  |  | $ 8.3 |  |
APS | Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Number of claims submitted | claim |  |  |  |  |  |  | 11 |
Gain contingency, number of settlement agreement time periods | timePeriod |  |  |  |  |  | 11 |  |
Settlement amount, awarded to company |  |  |  |  |  | $ 50.7 |  |
APS | Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal | Subsequent Event |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Settlement amount, sought | $ 4.5 |  |  |  |  |  |  |
NTEC | Four Corners |  |  |  |  |  |  |  |
Schedule of Commitments and Contingencies [Line Items] |  |  |  |  |  |  |  |
Asset purchase agreement, option to purchase, ownership interest, percentage |  |  |  | 7.00% |  |  |  |

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- Definition Represents the "all risk" (including nuclear hazards) insurance for property damage to, and decontamination of, property at Palo Verde of which a substantial portion must first be applied to stabilization and decontamination. + References No definition available. + Details
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