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Credit Agreement - Additional Information (Details) - Avista Utilities [Member] $ in Millions | 1 Months Ended
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Apr. 30, 2020 USD ($)
Short-term Debt [Line Items] |
Credit agreement amount borrowed | $ 100.0
Credit agreement, expiration month and year | 2021-04
Maximum borrowing capacity credit agreement | $ 100.0

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- Definition Line of credit facility, expiration month and year. + References No definition available. + Details
Name: | ava_LineOfCreditFacilityExpirationMonthAndYear
Namespace Prefix: | ava_
Data Type: | xbrli:gYearMonthItemType
Balance Type: | na
Period Type: | duration

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- Definition Maximum Borrowing Capacity Credit Agreement + References No definition available. + Details
Name: | ava_MaximumBorrowingCapacityCreditAgreement
Namespace Prefix: | ava_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of borrowings from a bank classified as other, maturing within one year or operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
Name: | us-gaap_ShortTermBankLoansAndNotesPayable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition 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. + References No definition available. + Details
Name: | us-gaap_ShortTermDebtLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=ava_AvistaUtilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |