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v3.20.4

Energy Purchase Contracts Additional Information (Details) | 12 Months Ended
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Dec. 31, 2020
Minimum [Member] |
Energy Purchase Contracts [Line Items] |
Remaining term of purchase contract | 1 month
Maximum [Member] |
Energy Purchase Contracts [Line Items] |
Remaining term of purchase contract | 25 years

X
- Definition Energy Purchase Contracts [Line Items] + References No definition available. + Details
Name: | ava_EnergyPurchaseContractsLineItems
Namespace Prefix: | ava_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Remaining term of purchase contract. + References No definition available. + Details
Name: | ava_RemainingTermOfPurchaseContract
Namespace Prefix: | ava_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |