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Loss contingency noneconomic damages.

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Number of actions on behalf of individual plaintiffs.

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Number of class action lawsuit.

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Number of collective bargaining agreement term.

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Number of plaintiffs.

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Number of private plaintiffs.

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Number of residential, commercial and other structures impacted.

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Number of subrogation actions filed.

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Percentage of employees represented.

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Percentage of largest group of employees represented.

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Road fire covered area.

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Amount of gain (loss) recognized in settlement of litigation and insurance claims. Excludes claims within an insurance entity's normal claims settlement process.

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Amount due in settlement of a claim for reimbursement from an insurance company when the Company has suffered a loss covered under an insurance policy.

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The proportionate share of interest (percent) in a jointly owned utility plant.

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Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2019 USD ($)	Dec. 31, 2024 USD ($) Plaintiff Lawsuit	Jul. 31, 2024	Aug. 31, 2023 a	Jan. 16, 2023	Sep. 30, 2020 a Structures
Loss Contingencies [Line Items]
Owners percentage interest		15.00%
Collective Bargaining Agreements Avista Utilities Employees [Member] \| IBEW [Member]
Loss Contingencies [Line Items]
Percentage of employees represented		36.00%
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
Unspecified Damages [Member]
Loss Contingencies [Line Items]
Number Of Plaintiffs \| Plaintiff		128
Boyds Fire [Member] \| Damage from Fire [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 4.4
Babb Road Fire [Member] \| Damage from Fire [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value		$ 21.0
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 class action lawsuit \| Lawsuit		1
Number of private plaintiffs \| Plaintiff		80
Damages claimed by private plaintiffs		$ 60.0
Noneconomic damages		21.0
Insurance settlements receivable		6.0
Colstrip [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Litigation settlement		$ 0.1
Orofino Fire [Member] \| Damage from Fire [Member]
Loss Contingencies [Line Items]
Road fire covered area \| a				53
Avista Corp [Member] \| Boyds Fire [Member] \| Property Damages [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	0.8
Avista Corp [Member] \| Boyds Fire [Member] \| Insurance proceeds paid to their insureds [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 1.8
PSE [Member] \| Colstrip [Member] \| Unit 3 [Member]
Loss Contingencies [Line Items]
Owners percentage interest		25.00%
PSE [Member] \| Colstrip [Member] \| Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest		25.00%	25.00%
NorthWestern [Member] \| Colstrip [Member] \| Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest		30.00%			15.00%