Derivatives and Risk Management - Additional Information (Details)	12 Months Ended
Dec. 31, 2020 USD ($) MWh MMBTU	Dec. 31, 2019 USD ($) MWh MMBTU
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]
Letters of credit outstanding \| $	$ 0	$ 0
Purchase [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Purchase [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0
Purchase [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Purchase [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0
Sales [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Sales [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0
Sales [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Sales [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0

Energy commodity derivative expected to be settle after year five.

No definition available.

Name:	ava_EnergyCommodityDerivativeExpectedToBeSettleAfterYearFive
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 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

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_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- 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
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SalesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Derivatives and Risk Management - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) MWh MMBTU	Dec. 31, 2019 USD ($) MWh MMBTU
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]
Letters of credit outstanding \| $	$ 0	$ 0
Purchase [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Purchase [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0
Purchase [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Purchase [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0
Sales [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Sales [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0
Sales [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0
Expected deliveries of energy commodity derivatives after three years \| MWh		0
Sales [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0
Expected deliveries of energy commodity derivatives after three years \| MMBTU		0