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Commitments and Contingencies - Additional Information (Details) $ in Thousands |  | 1 Months Ended | 3 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Apr. 15, 2025 USD ($) Claims Employees Chapter Plaintiff | Aug. 31, 2019 USD ($) | Mar. 31, 2025 USD ($) Plaintiff Lawsuit | Jul. 31, 2024 | Aug. 31, 2023 a | Jan. 16, 2023 | Sep. 30, 2020 a Structures
Collective Bargaining Agreements Avista Utilities Employees [Member] | IBEW [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of employees represented |  |  | 35.00% |  |  |  |
Collective Bargaining Agreements Avista Utilities Bargaining Unit Employees [Member] | IBEW [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of largest group of employees represented |  |  | 90.00% |  |  |  |
Collective Bargaining Agreements [Member] | IBEW [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Agreement term |  |  | 4 years |  |  |  |
Agreement expiration month and year |  |  | 2025-03 |  |  |  |
Collective Bargaining Agreements [Member] | IBEW [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
IBEW chapter | Chapter | 77 |  |  |  |  |  |
Number of employees comprised | Employees | 19 |  |  |  |  |  |
Damage from Fire [Member] | Settled in Principle [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Settlement Amount | $ 13,000 |  |  |  |  |  |
Boyds Fire [Member] | Damage from Fire [Member] | Maximum [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, damages sought, value |  | $ 4,000 |  |  |  |  |
Boyds Fire [Member] | Property Damages [Member] | Avista Corp [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, damages sought, value |  | 1,000 |  |  |  |  |
Boyds Fire [Member] | Insurance proceeds paid to their insureds [Member] | Avista Corp [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, damages sought, value |  | $ 2,000 |  |  |  |  |
Babb Road Fire [Member] | Damage from Fire [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Number of residential, commercial and other structures impacted | Structures |  |  |  |  |  |  | 220
Road fire covered area | a |  |  |  |  |  |  | 15,000
Number of subrogation actions filed | Lawsuit |  |  | 6 |  |  |  |
Number of actions on behalf of individual plaintiffs | Plaintiff |  |  | 5 |  |  |  |
Number Of Plaintiffs | Plaintiff |  |  | 128 |  |  |  |
Babb Road Fire [Member] | Damage from Fire [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Settlement Amount | 21,000 |  |  |  |  |  |
Total settlement amount | $ 27,000 |  |  |  |  |  |
Number Of Plaintiffs | Plaintiff | 128 |  |  |  |  |  |
Babb Road Fire [Member] | Damage from Fire [Member] | Widman Action [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Claim amount remains unsettled |  |  | $ 1,250 |  |  |  |
Estimate of liability related to claim |  |  | 100 |  |  |  |
Babb Road Fire [Member] | Damage from Fire [Member] | CN Utility Consulting [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Settlement Amount | $ 6,000 |  |  |  |  |  |
Babb Road Fire [Member] | Damage from Fire [Member] | Settled [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Total settlement amount | $ 14,000 |  |  |  |  |  |
Number of settle the claims | Claims | 48 |  |  |  |  |  |
Babb Road Fire [Member] | Damage from Fire [Member] | Settled in Principle [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Number of settle the claims | Claims | 77 |  |  |  |  |  |
Orofino Fire [Member] | Damage from Fire [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Road fire covered area | a |  |  |  |  | 53 |  |
Colstrip [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Settlement Amount |  |  | $ 1,000 |  |  |  |
Colstrip [Member] | PSE [Member] | Unit 4 [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Owners percentage interest |  |  | 25.00% | 25.00% |  |  |
Colstrip [Member] | NorthWestern [Member] | Unit 4 [Member] |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Owners percentage interest |  |  | 30.00% |  |  | 15.00% |

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