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v3.25.2

Long-Term Debt to Affiliated Trusts - Additional Information (Details) - USD ($) $ in Millions | 1 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 31, 2023 | Jun. 30, 2025 | Dec. 31, 2000
Debt Instrument [Line Items] |  |  |
Payments for repurchase of trust preferred securities |  |  | $ 10
1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | Avista Capital II [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Junior subordinated debenture issuance date |  | 1997 |
Principal amount |  | $ 52 |
Avista Corp [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Noncontrolling interest, ownership percentage by parent |  | 100.00% |
Trust Preferred Securities Subject to Mandatory Redemption [Member] | 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | Avista Capital II [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Principal amount |  | $ 50 |
Debt instrument, basis spread on variable rate | 1.137% |  |
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] |  |
Common Trust Securities [Member] | 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | Avista Capital II [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Principal amount |  | $ 2 |

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