<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>421</ContextCount>
  <ElementCount>505</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>124</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>20</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Consolidated Statements Of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>Consolidated Statements Of Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002000 - Statement - Consolidated Statements Of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements Of Comprehensive Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002501 - Statement - Consolidated Statements Of Comprehensive Income (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/ConsolidatedStatementsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>Consolidated Statements Of Comprehensive Income (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003501 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004000 - Statement - Consolidated Statements Of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements Of Cash Flows</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1005000 - Statement - Consolidated Statements Of Equity And Redeemable Noncontrolling Interests</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/ConsolidatedStatementsOfEquityAndRedeemableNoncontrollingInterests</Role>
      <ShortName>Consolidated Statements Of Equity And Redeemable Noncontrolling Interests</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Summary Of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary Of Significant Accounting Policies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - New Accounting Standards</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/NewAccountingStandards</Role>
      <ShortName>New Accounting Standards</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Variable Interest Entities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/VariableInterestEntities</Role>
      <ShortName>Variable Interest Entities</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Business Acquisitions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/BusinessAcquisitions</Role>
      <ShortName>Business Acquisitions</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Discontinued Operations Discontinued Operations (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.avistacorp.com/role/DiscontinuedOperationsDiscontinuedOperationsNotes</Role>
      <ShortName>Discontinued Operations Discontinued Operations (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Derivatives And Risk Management</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DerivativesAndRiskManagement</Role>
      <ShortName>Derivatives And Risk Management</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Pension Plans And Other Postretirement Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/PensionPlansAndOtherPostretirementBenefitPlans</Role>
      <ShortName>Pension Plans And Other Postretirement Benefit Plans</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - Committed Lines of Credit</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/CommittedLinesOfCredit</Role>
      <ShortName>Committed Lines of Credit</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2122100 - Disclosure - Long-Term Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/LongTermDebt</Role>
      <ShortName>Long-Term Debt</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2124100 - Disclosure - Fair Value</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/FairValue</Role>
      <ShortName>Fair Value</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2127100 - Disclosure - Earnings Per Common Share Attributable To Avista Corporation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/EarningsPerCommonShareAttributableToAvistaCorporation</Role>
      <ShortName>Earnings Per Common Share Attributable To Avista Corporation</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2128100 - Disclosure - Commitments And Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments And Contingencies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2129100 - Disclosure - Information By Business Segments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/InformationByBusinessSegments</Role>
      <ShortName>Information By Business Segments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Summary Of Significant Accounting Policies (Policy)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesPolicy</Role>
      <ShortName>Summary Of Significant Accounting Policies (Policy)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2301302 - Disclosure - Summary Of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary Of Significant Accounting Policies (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Business Acquisitions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/BusinessAcquisitionsTables</Role>
      <ShortName>Business Acquisitions (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Discontinued Operations Discontinued Operations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DiscontinuedOperationsDiscontinuedOperationsTables</Role>
      <ShortName>Discontinued Operations Discontinued Operations (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Derivatives And Risk Management (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DerivativesAndRiskManagementTables</Role>
      <ShortName>Derivatives And Risk Management (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - Pension Plans And Other Postretirement Benefit Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/PensionPlansAndOtherPostretirementBenefitPlansTables</Role>
      <ShortName>Pension Plans And Other Postretirement Benefit Plans (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2318301 - Disclosure - Committed Lines of Credit (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/CommittedLinesOfCreditTables</Role>
      <ShortName>Committed Lines of Credit (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2322301 - Disclosure - Long-Term Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/LongTermDebtTables</Role>
      <ShortName>Long-Term Debt (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2324301 - Disclosure - Fair Value (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/FairValueTables</Role>
      <ShortName>Fair Value (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2327301 - Disclosure - Earnings Per Common Share Attributable To Avista Corporation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/EarningsPerCommonShareAttributableToAvistaCorporationTables</Role>
      <ShortName>Earnings Per Common Share Attributable To Avista Corporation (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2329301 - Disclosure - Information By Business Segments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/InformationByBusinessSegmentsTables</Role>
      <ShortName>Information By Business Segments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2401403 - Disclosure - Summary Of Significant Accounting Policies (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2401404 - Disclosure - Summary Of Significant Accounting Policies (Utility Taxes) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesUtilityTaxesDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Utility Taxes) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2401405 - Disclosure - Summary Of Significant Accounting Policies (Other Income - Net) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesOtherIncomeNetDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Other Income - Net) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2401406 - Disclosure - Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesMaterialsAndSuppliesFuelStockAndNaturalGasStoredDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2401407 - Disclosure - Summary Of Significant Accounting Policies (Investments And Funds Held For Customers) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesInvestmentsAndFundsHeldForCustomersDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Investments And Funds Held For Customers) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2401408 - Disclosure - Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Disposition of Available-for-Sale Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfSignificantAccountingPoliciesDispositionOfAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Disposition of Available-for-Sale Securities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2401409 - Disclosure - Summary Of Significant Accounting Policies (Contractual Maturities Of Securities Available For Sale) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesContractualMaturitiesOfSecuritiesAvailableForSaleDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Contractual Maturities Of Securities Available For Sale) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2401410 - Disclosure - Summary Of Significant Accounting Policies (Goodwill) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesGoodwillDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Goodwill) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2401411 - Disclosure - Summary Of Significant Accounting Policies (Other Intangible Amortization) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesOtherIntangibleAmortizationDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Other Intangible Amortization) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2401413 - Disclosure - Summary Of Significant Accounting Policies (Accumulated Amortization Of Other Intangibles) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesAccumulatedAmortizationOfOtherIntangiblesDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Accumulated Amortization Of Other Intangibles) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2401414 - Disclosure - Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Accumulated Other Comprehensive Loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfSignificantAccountingPoliciesAccumulatedOtherComprehensiveLossDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Accumulated Other Comprehensive Loss) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2401415 - Disclosure - Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesReclassificationsOutOfAccumulatedOtherComprehensiveLossDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2401416 - Disclosure - Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Appropriated Retained Earnings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfSignificantAccountingPoliciesAppropriatedRetainedEarningsDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Appropriated Retained Earnings) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2401417 - Disclosure - Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Stock Repurchase Program) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfSignificantAccountingPoliciesStockRepurchaseProgramDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Stock Repurchase Program) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - Variable Interest Entities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/VariableInterestEntitiesDetails</Role>
      <ShortName>Variable Interest Entities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Business Acquisitions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/BusinessAcquisitionsDetails</Role>
      <ShortName>Business Acquisitions (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - Business Acquisitions Contract Price and Fair Value of Consideration Transferred (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/BusinessAcquisitionsContractPriceAndFairValueOfConsiderationTransferredDetails</Role>
      <ShortName>Business Acquisitions Contract Price and Fair Value of Consideration Transferred (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2407404 - Disclosure - Business Acquisitions Assets Acquired Liabilities Assumed (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/BusinessAcquisitionsAssetsAcquiredLiabilitiesAssumedDetails</Role>
      <ShortName>Business Acquisitions Assets Acquired Liabilities Assumed (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2407405 - Disclosure - Business Acquisitions Pro Forma Operating Results (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/BusinessAcquisitionsProFormaOperatingResultsDetails</Role>
      <ShortName>Business Acquisitions Pro Forma Operating Results (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Discontinued Operations Summary of Cash Proceeds from Sale of Discontinued Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DiscontinuedOperationsSummaryOfCashProceedsFromSaleOfDiscontinuedOperationsDetails</Role>
      <ShortName>Discontinued Operations Summary of Cash Proceeds from Sale of Discontinued Operations (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Discontinued Operations Summary of Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DiscontinuedOperationsSummaryOfAssetsAndLiabilitiesDetails</Role>
      <ShortName>Discontinued Operations Summary of Assets and Liabilities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - Discontinued Operations Summary of Income Statement Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DiscontinuedOperationsSummaryOfIncomeStatementInformationDetails</Role>
      <ShortName>Discontinued Operations Summary of Income Statement Information (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Derivatives And Risk Management (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DerivativesAndRiskManagementNarrativeDetails</Role>
      <ShortName>Derivatives And Risk Management (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Derivatives And Risk Management (Energy Commodity Derivatives) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DerivativesAndRiskManagementEnergyCommodityDerivativesDetails</Role>
      <ShortName>Derivatives And Risk Management (Energy Commodity Derivatives) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2414404 - Disclosure - Derivatives And Risk Management (Interest Rate Swap Agreements) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DerivativesAndRiskManagementInterestRateSwapAgreementsDetails</Role>
      <ShortName>Derivatives And Risk Management (Interest Rate Swap Agreements) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2414405 - Disclosure - Derivatives And Risk Management (Derivative Instruments Summary) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DerivativesAndRiskManagementDerivativeInstrumentsSummaryDetails</Role>
      <ShortName>Derivatives And Risk Management (Derivative Instruments Summary) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2414406 - Disclosure - Derivatives And Risk Management Derivatives and Risk Management (Foreign Currency Exchange Contracts) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/DerivativesAndRiskManagementDerivativesAndRiskManagementForeignCurrencyExchangeContractsDetails</Role>
      <ShortName>Derivatives And Risk Management Derivatives and Risk Management (Foreign Currency Exchange Contracts) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - Pension Plans And Other Postretirement Benefit Plans (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/PensionPlansAndOtherPostretirementBenefitPlansNarrativeDetails</Role>
      <ShortName>Pension Plans And Other Postretirement Benefit Plans (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2415403 - Disclosure - Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/PensionPlansAndOtherPostretirementBenefitPlansComponentsOfNetPeriodicBenefitCostDetails</Role>
      <ShortName>Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2418402 - Disclosure - Committed Lines of Credit (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/CommittedLinesOfCreditDetails</Role>
      <ShortName>Committed Lines of Credit (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2422402 - Disclosure - Long-Term Debt (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/LongTermDebtNarrativeDetails</Role>
      <ShortName>Long-Term Debt (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2422403 - Disclosure - Long-Term Debt (Schedule Of Long-Term Debt Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/LongTermDebtScheduleOfLongTermDebtInstrumentsDetails</Role>
      <ShortName>Long-Term Debt (Schedule Of Long-Term Debt Instruments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2422404 - Disclosure - Long-Term Debt (Schedule Of Long-Term Debt Maturities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/LongTermDebtScheduleOfLongTermDebtMaturitiesDetails</Role>
      <ShortName>Long-Term Debt (Schedule Of Long-Term Debt Maturities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2424402 - Disclosure - Fair Value (Carrying Value And Estimated Fair Value Of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/FairValueCarryingValueAndEstimatedFairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value (Carrying Value And Estimated Fair Value Of Financial Instruments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2424403 - Disclosure - Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/FairValueFairValueOfAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails</Role>
      <ShortName>Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2424404 - Disclosure - Fair Value (Quantitative Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/FairValueQuantitativeInformationDetails</Role>
      <ShortName>Fair Value (Quantitative Information) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2424405 - Disclosure - Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/FairValueReconciliationForAllAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisUsingSignificantUnobservableInputsLevel3Details</Role>
      <ShortName>Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2427402 - Disclosure - Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/EarningsPerShareAttributableToAvistaCorporationComputationOfEarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2428401 - Disclosure - Commitments And Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments And Contingencies (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2429402 - Disclosure - Information By Business Segments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.avistacorp.com/role/InformationByBusinessSegmentsDetails</Role>
      <ShortName>Information By Business Segments (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element ava_DiscontinuedOperationTransactionExpenses had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element ava_EscrowReceivable had a mix of decimals attribute values: -5 -4.</Log>
    <Log type="Info">Element ava_EvaluatedPowerCapacity had a mix of decimals attribute values: 0 1.</Log>
    <Log type="Info">Element us-gaap_CashAndCashEquivalentsAtCarryingValue had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_CommonStockDividendsPerShareCashPaid had a mix of decimals attribute values: 3 4.</Log>
    <Log type="Info">Element us-gaap_DerivativeFairValueAmountOffsetAgainstCollateralNet had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_DerivativePriceRiskOptionStrikePrice had a mix of decimals attribute values: 1 2.</Log>
    <Log type="Info">Element us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity had a mix of decimals attribute values: -6 -5.</Log>
    <Log type="Info">Element us-gaap_PaymentsForProceedsFromDerivativeInstrumentFinancingActivities had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_StockRepurchasedDuringPeriodShares had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">'Monetary' elements on report '2401403 - Disclosure - Summary Of Significant Accounting Policies (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Shares' elements on report '2401417 - Disclosure - Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Stock Repurchase Program) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2407402 - Disclosure - Business Acquisitions (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2407405 - Disclosure - Business Acquisitions Pro Forma Operating Results (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2411402 - Disclosure - Discontinued Operations Summary of Cash Proceeds from Sale of Discontinued Operations (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2411404 - Disclosure - Discontinued Operations Summary of Income Statement Information (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2414402 - Disclosure - Derivatives And Risk Management (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2414404 - Disclosure - Derivatives And Risk Management (Interest Rate Swap Agreements) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2414405 - Disclosure - Derivatives And Risk Management (Derivative Instruments Summary) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2415402 - Disclosure - Pension Plans And Other Postretirement Benefit Plans (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2418402 - Disclosure - Committed Lines of Credit (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2422402 - Disclosure - Long-Term Debt (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2428401 - Disclosure - Commitments And Contingencies (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - Consolidated Statements Of Income</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - Consolidated Statements Of Comprehensive Income</Log>
    <Log type="Info">Process Flow-Through: 1002501 - Statement - Consolidated Statements Of Comprehensive Income (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Consolidated Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Sep. 30, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2012'</Log>
    <Log type="Info">Process Flow-Through: 1003501 - Statement - Consolidated Balance Sheets (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1004000 - Statement - Consolidated Statements Of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>ava-20140930.xml</File>
    <File>ava-20140930.xsd</File>
    <File>ava-20140930_cal.xml</File>
    <File>ava-20140930_def.xml</File>
    <File>ava-20140930_lab.xml</File>
    <File>ava-20140930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
