Amount Of First Mortgage Bonds That Could Be Issued

No definition available.

Name:	ava_AmountOfFirstMortgageBondsThatCouldBeIssued
Namespace Prefix:	ava_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of First Mortgage Bonds that Could be Issued, Percent

+ References

No definition available.

+ Details

Name:	ava_AmountOfFirstMortgageBondsThatCouldBeIssuedPercent
Namespace Prefix:	ava_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

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

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ava_AvistaUtilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_FirstMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ava_AlaskaElectricLightPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ava_DerivativesCashSettlementDateAxis=ava_TwoThousandNineteenMember
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:

Long-Term Debt (Narrative) (Details) $ in Thousands	12 Months Ended
Long-Term Debt (Narrative) (Details) $ in Thousands	Dec. 31, 2019 USD ($) Caontracts	Dec. 31, 2018 USD ($)	Dec. 31, 2017
Debt Instrument [Line Items]
Secured Debt	$ 1,979,200	$ 1,889,200
Debt Instrument, Interest Rate, Stated Percentage	2.79%	3.61%	2.36%
Avista Utilities [Member]
Debt Instrument [Line Items]
Secured Debt	$ 1,904,200	$ 1,814,200
Avista Utilities [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount Of First Mortgage Bonds That Could Be Issued	$ 1,500,000
Alaska Electric Light & Power [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount Of First Mortgage Bonds That Could Be Issued	$ 30,400
2019 \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Settled Derivative Notional Amount	$ 70,000
Number of Interest Rate Swaps Settled \| Caontracts	6