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Energy Purchase Contracts Additional Information (Details)	12 Months Ended
	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

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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: