<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>214</ContextCount>
  <ElementCount>473</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>73</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/StatementBalanceSheets</Role>
      <ShortName>Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/StatementBalanceSheetsParenthetical</Role>
      <ShortName>Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100030 - Statement - Statements of Operations and Comprehensive Loss</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/StatementStatementsOfOperationsAndComprehensiveLoss</Role>
      <ShortName>Statements of Operations and Comprehensive Loss</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100040 - Statement - Statements of Convertible Preferred Stock/Units and Stockholders'/Members' Equity (Deficit)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/StatementStatementsOfConvertiblePreferredStockUnitsAndStockholdersMembersEquityDeficit</Role>
      <ShortName>Statements of Convertible Preferred Stock/Units and Stockholders'/Members' Equity (Deficit)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100050 - Statement - Statements of Convertible Preferred Stock/Units and Stockholders'/Members' Equity (Deficit) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/StatementStatementsOfConvertiblePreferredStockUnitsAndStockholdersMembersEquityDeficitParenthetical</Role>
      <ShortName>Statements of Convertible Preferred Stock/Units and Stockholders'/Members' Equity (Deficit) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100060 - Statement - Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/StatementStatementsOfCashFlows</Role>
      <ShortName>Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100070 - Disclosure - Description of Business and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureDescriptionOfBusinessAndBasisOfPresentation</Role>
      <ShortName>Description of Business and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Marketable Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureMarketableSecurities</Role>
      <ShortName>Marketable Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100110 - Disclosure -  Collaboration, License and Research Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCollaborationLicenseAndResearchAgreements</Role>
      <ShortName>Collaboration, License and Research Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Property and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosurePropertyAndEquipment</Role>
      <ShortName>Property and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureDebt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Convertible Notes</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureConvertibleNotes</Role>
      <ShortName>Convertible Notes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Stockholders' Equity (Deficit)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficit</Role>
      <ShortName>Stockholders' Equity (Deficit)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100170 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100180 - Disclosure - COVID-19</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCOVID19</Role>
      <ShortName>COVID-19</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100190 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100230 - Disclosure - Marketable Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureMarketableSecuritiesTables</Role>
      <ShortName>Marketable Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureMarketableSecurities</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100240 - Disclosure -  Collaboration, License and Research Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCollaborationLicenseAndResearchAgreementsTables</Role>
      <ShortName>Collaboration, License and Research Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCollaborationLicenseAndResearchAgreements</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Property and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosurePropertyAndEquipmentTables</Role>
      <ShortName>Property and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosurePropertyAndEquipment</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100260 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100270 - Disclosure - Stockholders' Equity (Deficit) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitTables</Role>
      <ShortName>Stockholders' Equity (Deficit) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficit</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureIncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureIncomeTaxes</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Description of Business and Basis of Presentation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureDescriptionOfBusinessAndBasisOfPresentationAdditionalInformationDetails</Role>
      <ShortName>Description of Business and Basis of Presentation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100300 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share/Unit (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfPotentiallyDilutiveSecuritiesNotIncludedInCalculationOfDilutedNetLossPerShareUnitDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share/Unit (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Fair Value Measurements - Summary of Cash Equivalents and Marketable Securities Measured at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfCashEquivalentsAndMarketableSecuritiesMeasuredAtFairValueDetails</Role>
      <ShortName>Fair Value Measurements - Summary of Cash Equivalents and Marketable Securities Measured at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100330 - Disclosure - Fair Value Measurements - Schedule of Reconciliation of Preferred Stock Warrant Liability Measured at Fair Value Using Level 3 Unobservable Inputs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureFairValueMeasurementsScheduleOfReconciliationOfPreferredStockWarrantLiabilityMeasuredAtFairValueUsingLevel3UnobservableInputsDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Reconciliation of Preferred Stock Warrant Liability Measured at Fair Value Using Level 3 Unobservable Inputs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100340 - Disclosure - Marketable Securities - Summary of Marketable Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureMarketableSecuritiesSummaryOfMarketableSecuritiesDetails</Role>
      <ShortName>Marketable Securities - Summary of Marketable Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100350 - Disclosure - Collaboration, License and Research Agreements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCollaborationLicenseAndResearchAgreementsAdditionalInformationDetails</Role>
      <ShortName>Collaboration, License and Research Agreements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Collaboration, License and Research Agreements - Reconciliation of Deferred Revenue Related to Lilly Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCollaborationLicenseAndResearchAgreementsReconciliationOfDeferredRevenueRelatedToLillyAgreementDetails</Role>
      <ShortName>Collaboration, License and Research Agreements - Reconciliation of Deferred Revenue Related to Lilly Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>100370 - Disclosure - Property,and Equipment - Schedule of Property and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetails</Role>
      <ShortName>Property,and Equipment - Schedule of Property and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>100380 - Disclosure - Property and Equipment - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosurePropertyAndEquipmentAdditionalInformationDetails</Role>
      <ShortName>Property and Equipment - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>100390 - Disclosure - Debt - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureDebtAdditionalInformationDetails</Role>
      <ShortName>Debt - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>100400 - Disclosure - Convertible Notes - Additional Information (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureConvertibleNotesAdditionalInformationDetails</Role>
      <ShortName>Convertible Notes - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>100410 - Disclosure - Commitments and Contingencies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetails</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>100420 - Disclosure - Commitments and Contingencies - Schedule of ROU Assets and Liabilities Related to 2014 Lease and Temporary Lease (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingenciesScheduleOfROUAssetsAndLiabilitiesRelatedTo2014LeaseAndTemporaryLeaseDetails</Role>
      <ShortName>Commitments and Contingencies - Schedule of ROU Assets and Liabilities Related to 2014 Lease and Temporary Lease (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>100430 - Disclosure - Commitments and Contingencies - Schedule of Maturities of Lease Liabilities due under 2014 Lease and Temporary Lease (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingenciesScheduleOfMaturitiesOfLeaseLiabilitiesDueUnder2014LeaseAndTemporaryLeaseDetails</Role>
      <ShortName>Commitments and Contingencies - Schedule of Maturities of Lease Liabilities due under 2014 Lease and Temporary Lease (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>100450 - Disclosure - Commitments and Contingencies - Supplemental Cash Flow Information Related to Cash Paid for Amounts Included in Measurement of Operating Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingenciesSupplementalCashFlowInformationRelatedToCashPaidForAmountsIncludedInMeasurementOfOperatingLeaseLiabilitiesDetails</Role>
      <ShortName>Commitments and Contingencies - Supplemental Cash Flow Information Related to Cash Paid for Amounts Included in Measurement of Operating Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>100460 - Disclosure - Commitments and Contingencies - Schedule of Rent Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureCommitmentsAndContingenciesScheduleOfRentExpenseDetails</Role>
      <ShortName>Commitments and Contingencies - Schedule of Rent Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>100470 - Disclosure - Stockholders' Equity (Deficit) - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitAdditionalInformationDetails</Role>
      <ShortName>Stockholders' Equity (Deficit) - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>100480 - Disclosure - Stockholders' Equity (Deficit) - Summary of Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitSummaryOfStockOptionActivityDetails</Role>
      <ShortName>Stockholders' Equity (Deficit) - Summary of Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>100490 - Disclosure - Stockholders' Equity (Deficit) - Schedule of Assumptions used in Black-Scholes Model to Determine Fair Value of Stock/Unit Option Grants and Shares Purchasable under ESPP (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitScheduleOfAssumptionsUsedInBlackScholesModelToDetermineFairValueOfStockUnitOptionGrantsAndSharesPurchasableUnderESPPDetails</Role>
      <ShortName>Stockholders' Equity (Deficit) - Schedule of Assumptions used in Black-Scholes Model to Determine Fair Value of Stock/Unit Option Grants and Shares Purchasable under ESPP (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>100500 - Disclosure - Stockholders' Equity (Deficit) - Schedule of Allocated Stock-based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitScheduleOfAllocatedStockBasedCompensationExpenseDetails</Role>
      <ShortName>Stockholders' Equity (Deficit) - Schedule of Allocated Stock-based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>100510 - Disclosure - Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitScheduleOfCommonStockReservedForFutureIssuanceDetails</Role>
      <ShortName>Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureStockholdersEquityDeficitTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>100520 - Disclosure - Income Taxes - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetails</Role>
      <ShortName>Income Taxes - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>100530 - Disclosure - Income Taxes - Reconciliation of Income Taxes Computed by Applying Statutory Federal Income Tax Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureIncomeTaxesReconciliationOfIncomeTaxesComputedByApplyingStatutoryFederalIncomeTaxRateDetails</Role>
      <ShortName>Income Taxes - Reconciliation of Income Taxes Computed by Applying Statutory Federal Income Tax Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>100540 - Disclosure - Income Taxes - Components of Deferred Tax Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureIncomeTaxesComponentsOfDeferredTaxAssetsDetails</Role>
      <ShortName>Income Taxes - Components of Deferred Tax Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>100550 - Disclosure - Income Taxes - Summarizes of Activity Related to Gross Unrecognized Tax Benefits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureIncomeTaxesSummarizesOfActivityRelatedToGrossUnrecognizedTaxBenefitsDetails</Role>
      <ShortName>Income Taxes - Summarizes of Activity Related to Gross Unrecognized Tax Benefits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="rna-10k_20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>100560 - Disclosure - Subsequent Events - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aviditybiosciences.com/20211231/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetails</Role>
      <ShortName>Subsequent Events - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-K" original="rna-10k_20211231.htm">rna-10k_20211231.htm</File>
    <File>rna-20211231.xsd</File>
    <File>rna-20211231_cal.xml</File>
    <File>rna-20211231_def.xml</File>
    <File>rna-20211231_lab.xml</File>
    <File>rna-20211231_pre.xml</File>
    <File>rna-ex1012_82.htm</File>
    <File>rna-ex231_8.htm</File>
    <File>rna-ex311_9.htm</File>
    <File>rna-ex312_6.htm</File>
    <File>rna-ex321_10.htm</File>
    <File>rna-ex322_7.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>gsua0c5v34oe000001.jpg</File>
    <File>gsua0c5v34oe000002.jpg</File>
    <File>gsua0c5v34oe000003.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="701">http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy items="37">http://xbrl.sec.gov/dei/2021q4</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
