Energy commodity derivative expected to be settle after year four.

No definition available.

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Namespace Prefix:	ava_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Energy commodity derivative expected to be settle after year three.

+ References

No definition available.

+ Details

Name:	ava_EnergyCommodityDerivativeExpectedToBeSettleAfterYearThree
Namespace Prefix:	ava_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of interest rate swaps settled.

+ References

No definition available.

+ Details

Name:	ava_NumberOfInterestRateSwapsSettled
Namespace Prefix:	ava_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of period currency prices are settled with domestic country currency.

+ References

No definition available.

+ Details

Name:	ava_NumberOfPeriodCurrencyPricesAreSettledWithDomesticCountryCurrency
Namespace Prefix:	ava_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Payments for (proceeds from) derivative instrument operating activities.

+ References

No definition available.

+ Details

Name:	ava_PaymentsForProceedsFromDerivativeInstrumentOperatingActivities
Namespace Prefix:	ava_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Settled derivative notional amount.

+ References

No definition available.

+ Details

Name:	ava_SettledDerivativeNotionalAmount
Namespace Prefix:	ava_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

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Period Type:	duration

- Details

Name:	srt_StatementGeographicalAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ava_PurchaseMember
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Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ava_PhysicalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_EnergyAxis=ava_ElectricDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_EnergyAxis=ava_GasDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ava_FinancialMember
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Data Type:	na
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- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SalesMember
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Derivatives and Risk Management - Additional Information (Details)		1 Months Ended	9 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) Contract	Jul. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) MWh MMBTU	Sep. 30, 2019 USD ($)	Dec. 31, 2019 MWh MMBTU
Derivative [Line Items]
Payments for (proceeds from) derivative instrument operating activities \| $			$ 33,499,000	$ 13,325,000
Canadian [Member]
Derivative [Line Items]
Number of days Canadian currency prices are settled with U.S. dollars			60 days
Interest Rate Swap [Member]
Derivative [Line Items]
Number of interest rate swaps settled \| Contract	7
Settled derivative notional amount \| $	$ 70,000,000.0
Payments for (proceeds from) derivative instrument operating activities \| $		$ 33,500,000
Purchase [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MWh			0
Expected deliveries of energy commodity derivatives after 2022 \| MWh					0
Purchase [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MMBTU			0
Expected deliveries of energy commodity derivatives after 2022 \| MMBTU					0
Purchase [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MWh			0
Expected deliveries of energy commodity derivatives after 2022 \| MWh					0
Purchase [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MMBTU			0
Expected deliveries of energy commodity derivatives after 2022 \| MMBTU					0
Sales [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MWh			0
Expected deliveries of energy commodity derivatives after 2022 \| MWh					0
Sales [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MMBTU			0
Expected deliveries of energy commodity derivatives after 2022 \| MMBTU					0
Sales [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MWh			0
Expected deliveries of energy commodity derivatives after 2022 \| MWh					0
Sales [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after 2023 \| MMBTU			0
Expected deliveries of energy commodity derivatives after 2022 \| MMBTU					0