Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/exampleRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
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Commitments and Contingencies - Additional Information (Details) $ in Millions		1 Months Ended		9 Months Ended
	Apr. 15, 2025 Chapter Employees	Jul. 31, 2026 USD ($)	Aug. 31, 2023 USD ($) a	Sep. 30, 2026
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]
IBEW chapter \| Chapter	77
Agreement term				4 years
Agreement expiration year				2029
Number of employees comprised \| Employees	20
Orofino Fire [Member] \| Damage from Fire [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value			$ 0.2
Road fire covered area \| a			53
Rathdrum, Idaho Natural Gas Incident [Member]
Loss Contingencies [Line Items]
Estimate of liability related to claim		$ 1.3
Loss Contingency Settlement Agreement Period		2026-08