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%