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Energy Purchase Contracts (Schedule Of Utility Total Expenses) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Energy Purchase Contracts [Abstract] |  |  |
Utility power resources | $ 376,769 | $ 357,656 | $ 380,523

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- Definition Energy Purchase Contracts + References No definition available. + Details
Name: | ava_EnergyPurchaseContractsAbstract
Namespace Prefix: | ava_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The total amount of power purchased, natural gas purchased, fuel for generation and other fuel costs, which are included in utility resource costs in the Consolidated Statements of Income + References No definition available. + Details
Name: | ava_UtilityPowerResources
Namespace Prefix: | ava_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration