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Long-Term Debt (Schedule Of Long-Term Debt Instruments) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Debt Instrument [Line Items]    
Secured and Unsecured Debt $ 1,526,700ava_SecuredandUnsecuredDebt $ 1,526,700ava_SecuredandUnsecuredDebt
Secured Debt 1,511,700us-gaap_SecuredDebt 1,511,700us-gaap_SecuredDebt
Other long-term debt and capital leases 1,495,546us-gaap_LongTermDebtAndCapitalLeaseObligations 1,492,062us-gaap_LongTermDebtAndCapitalLeaseObligations
Settled interest rate swaps (17,439)ava_SettledInterestRateSwaps (17,541)ava_SettledInterestRateSwaps
Unamortized debt discount (1,081)us-gaap_DebtInstrumentUnamortizedDiscount (1,122)us-gaap_DebtInstrumentUnamortizedDiscount
Total 1,582,378ava_LongTermDebtBeforeCurrentPortionAndBondsHeldByCompany 1,582,186ava_LongTermDebtBeforeCurrentPortionAndBondsHeldByCompany
Pollution Control Bonds (83,700)us-gaap_LongTermPollutionControlBond [1] (83,700)us-gaap_LongTermPollutionControlBond [1]
Other Long-term Debt and Capital Lease Obligations 74,198ava_OtherLongTermDebtAndCapitalLeaseObligations 74,149ava_OtherLongTermDebtAndCapitalLeaseObligations
Long-term Debt and Capital Lease Obligations, Current (3,132)us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent (6,424)us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent
Document Period End Date Mar. 31, 2015  
2018, 7.39% - 7.45% [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Interest Rate, minimum 7.39%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandEighteenSevenPointThreeNinePercentageToSevenPointFourFivePercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
Interest Rate, maximum 7.45%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandEighteenSevenPointThreeNinePercentageToSevenPointFourFivePercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
2023, 7.18% - 7.54% [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Interest Rate, minimum 7.18%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyThreeSevenPointOneEightPercentageToSevenPointFiveFourPercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
Interest Rate, maximum 7.54%us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyThreeSevenPointOneEightPercentageToSevenPointFiveFourPercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
2032 [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Pollution Control Bonds 66,700us-gaap_LongTermPollutionControlBond
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyTwoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
2034 [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Pollution Control Bonds 17,000us-gaap_LongTermPollutionControlBond
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
Avista Utilities [Member]    
Debt Instrument [Line Items]    
Secured Debt 1,436,700us-gaap_SecuredDebt
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 1,436,700us-gaap_SecuredDebt
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2018, 5.95% [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2018  
Debt instrument, interest rate, stated percentage 5.95%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandEighteenFivePointNineFivePercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 250,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandEighteenFivePointNineFivePercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 250,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandEighteenFivePointNineFivePercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2018, 7.39% - 7.45% [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Maturity Year 2018  
Medium-Term Notes, Noncurrent 22,500us-gaap_MediumtermNotesNoncurrent
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandEighteenSevenPointThreeNinePercentageToSevenPointFourFivePercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 22,500us-gaap_MediumtermNotesNoncurrent
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandEighteenSevenPointThreeNinePercentageToSevenPointFourFivePercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2019 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2019  
Debt instrument, interest rate, stated percentage 5.45%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandNineteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 90,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandNineteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 90,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandNineteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2020 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2020  
Debt instrument, interest rate, stated percentage 3.89%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 52,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 52,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2022 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2022  
Debt instrument, interest rate, stated percentage 5.13%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyTwoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 250,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyTwoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 250,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyTwoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2023, 7.18% - 7.54% [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Maturity Year 2023  
Medium-Term Notes, Noncurrent 13,500us-gaap_MediumtermNotesNoncurrent
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyThreeSevenPointOneEightPercentageToSevenPointFiveFourPercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 13,500us-gaap_MediumtermNotesNoncurrent
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyThreeSevenPointOneEightPercentageToSevenPointFiveFourPercentageMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2028 [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Maturity Year 2028  
Debt instrument, interest rate, stated percentage 6.37%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyEightMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Medium-Term Notes, Noncurrent 25,000us-gaap_MediumtermNotesNoncurrent
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyEightMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 25,000us-gaap_MediumtermNotesNoncurrent
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandTwentyEightMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2032 [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Maturity Year 2032 [1]  
Pollution Control Bonds 66,700us-gaap_LongTermPollutionControlBond
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyTwoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 [1] 66,700us-gaap_LongTermPollutionControlBond
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyTwoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 [1]
Avista Utilities [Member] | 2034 [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Maturity Year 2034 [1]  
Pollution Control Bonds 17,000us-gaap_LongTermPollutionControlBond
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 [1] 17,000us-gaap_LongTermPollutionControlBond
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 [1]
Avista Utilities [Member] | 2035 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2035  
Debt instrument, interest rate, stated percentage 6.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyFiveMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 150,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyFiveMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 150,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtyFiveMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2037 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2037  
Debt instrument, interest rate, stated percentage 5.70%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtySevenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 150,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtySevenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 150,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandThirtySevenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2040 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2040  
Debt instrument, interest rate, stated percentage 5.55%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 35,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 35,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2041 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2041  
Debt instrument, interest rate, stated percentage 4.45%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 85,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 85,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2047 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2047  
Debt instrument, interest rate, stated percentage 4.23%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortySevenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 80,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortySevenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 80,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortySevenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2016 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2016  
Debt instrument, interest rate, stated percentage 0.84%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandSixteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 90,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandSixteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 90,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandSixteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Avista Utilities [Member] | 2044 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2044  
Debt instrument, interest rate, stated percentage 4.11%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		  
Secured Debt 60,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember		 60,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AvistaUtilitiesMember
Alaska Electric Light & Power [Member] | 2044 [Member] | First Mortgage Bonds [Member]    
Debt Instrument [Line Items]    
Maturity Year 2044  
Debt instrument, interest rate, stated percentage 4.54%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AlaskaElectricLightPowerMember		  
Secured Debt 75,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AlaskaElectricLightPowerMember		 [2] 75,000us-gaap_SecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandFortyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_FirstMortgageMember
/ us-gaap_StatementBusinessSegmentsAxis
= ava_AlaskaElectricLightPowerMember		 [2]
Alaska Energy Resources Company [Member] | 2019 [Member] | Unsecured Debt [Member]    
Debt Instrument [Line Items]    
Maturity Year 2019  
Debt instrument, interest rate, stated percentage 3.85%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandNineteenMember
/ dei_LegalEntityAxis
= ava_AlaskaEnergyResourcesCompanyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		  
Unsecured Debt $ 15,000us-gaap_UnsecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandNineteenMember
/ dei_LegalEntityAxis
= ava_AlaskaEnergyResourcesCompanyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		 $ 15,000us-gaap_UnsecuredDebt
/ us-gaap_DebtInstrumentAxis
= ava_TwoThousandNineteenMember
/ dei_LegalEntityAxis
= ava_AlaskaEnergyResourcesCompanyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
[1] In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Condensed Consolidated Balance Sheets.
[2] Upon settlement of interest rate swaps, these are recorded as a regulatory asset or liability and included as part of long-term debt above. They are amortized as a component of interest expense over the life of the associated debt and included as a part of the Company's cost of debt calculation for ratemaking purposes.