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Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Gross Asset $ 97,940us-gaap_DerivativeFairValueOfDerivativeAsset $ 99,045us-gaap_DerivativeFairValueOfDerivativeAsset    
Liability 250,991us-gaap_DerivativeFairValueOfDerivativeLiability 229,790us-gaap_DerivativeFairValueOfDerivativeLiability    
Cash and cash equivalents 22,081us-gaap_CashAndCashEquivalentsAtCarryingValue 22,143us-gaap_CashAndCashEquivalentsAtCarryingValue 90,172us-gaap_CashAndCashEquivalentsAtCarryingValue 82,574us-gaap_CashAndCashEquivalentsAtCarryingValue
Fixed Income Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Cash and cash equivalents 800us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_FixedIncomeSecuritiesMember
800us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_FixedIncomeSecuritiesMember
   
Fair Value, Measurements, Recurring [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset (96,361)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(97,060)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Interest rate swaps   460us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Funds held in trust account of Spokane Energy   1,600us-gaap_AssetsHeldInTrust
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Total 9,678us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
11,452us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset (154,295)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(141,450)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Interest rate swaps 62,345us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
48,182us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Total 96,696us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
88,340us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset   (506)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset (50,490)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(29,386)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Energy commodity derivatives [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset (95,557)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(95,204)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Asset 762us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
1,525us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset (103,001)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(110,714)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability 8,187us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
16,380us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Natural Gas Exchange Agreements [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset (790)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(1,349)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Asset 817us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset (790)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(1,349)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability 0us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
35us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_NaturalGasExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Power Exchange Agreements [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset 0us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability 25,903us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
23,299us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerExchangeAgreementsMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Power Option Agreement [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset 0us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerOptionAgreementMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerOptionAgreementMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability 251us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerOptionAgreementMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
424us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= ava_PowerOptionAgreementMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Foreign Exchange Contract [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset (14)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(1)us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Asset 0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset (14)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
(1)us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivative Liability 10us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
20us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Deferred compensation assets: 1,866us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeSecuritiesMember
1,793us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeSecuritiesMember
   
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Deferred compensation assets: 6,233us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
6,074us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
   
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Funds held in trust account of Spokane Energy   1,600us-gaap_AssetsHeldInTrust
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Total 8,099us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
9,467us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Total 0us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Fixed Income Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Deferred compensation assets: 1,866us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeSecuritiesMember
1,793us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeSecuritiesMember
   
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Deferred compensation assets: 6,233us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
6,074us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
   
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Interest rate swaps   966us-gaap_InterestRateDerivativeAssetsAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Total 96,333us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
97,696us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Interest rate swaps 112,835us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
77,568us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Total 224,047us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
204,683us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Energy commodity derivatives [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Gross Asset 96,319us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
96,729us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Liability 111,188us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
127,094us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Exchange Contract [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Gross Asset 14us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
1us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Liability 24us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
21us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Total 1,607us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
1,349us-gaap_AssetsFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Total 26,944us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
25,107us-gaap_LiabilitiesFairValueDisclosureRecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Natural Gas Exchange Agreements [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Gross Asset 1,607us-gaap_DerivativeFairValueOfDerivativeAsset
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= us-gaap_FairValueMeasurementsRecurringMember
1,349us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
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/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Liability 790us-gaap_DerivativeFairValueOfDerivativeLiability
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/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
1,384us-gaap_DerivativeFairValueOfDerivativeLiability
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/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Exchange Agreements [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Liability 25,903us-gaap_DerivativeFairValueOfDerivativeLiability
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23,299us-gaap_DerivativeFairValueOfDerivativeLiability
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Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Option Agreement [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Liability $ 251us-gaap_DerivativeFairValueOfDerivativeLiability
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= ava_PowerOptionAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
$ 424us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
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/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
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