<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.24.2.u1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>218</ContextCount>
  <ElementCount>245</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>60</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Statement - Condensed Consolidated Balance Sheets (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedStatementsofOperationsandComprehensiveIncomeLossUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedStatementsofOperationsandComprehensiveIncomeLossUnauditedParenthetical</Role>
      <ShortName>Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedStatementsofStockholdersEquityUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedStatementsofStockholdersEquityUnauditedParenthetical</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952157 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedStatementsofCashFlowsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CondensedConsolidatedStatementsofCashFlowsUnauditedParenthetical</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/SignificantAccountingPolicies</Role>
      <ShortName>Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Marketable Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/MarketableSecurities</Role>
      <ShortName>Marketable Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - Acquisition and Research Funding Collaboration Agreement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/AcquisitionandResearchFundingCollaborationAgreement</Role>
      <ShortName>Acquisition and Research Funding Collaboration Agreement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Collaboration Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CollaborationAgreements</Role>
      <ShortName>Collaboration Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CommitmentsandContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Common Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CommonStock</Role>
      <ShortName>Common Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Stock-Based Awards</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/StockBasedAwards</Role>
      <ShortName>Stock-Based Awards</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Net Income (Loss) Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/NetIncomeLossPerShare</Role>
      <ShortName>Net Income (Loss) Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Divestiture of Preclinical Small Molecule Programs</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/DivestitureofPreclinicalSmallMoleculePrograms</Role>
      <ShortName>Divestiture of Preclinical Small Molecule Programs</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9954471 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/SignificantAccountingPoliciesPolicies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/SignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9954472 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/FairValueMeasurements</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9954473 - Disclosure - Marketable Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/MarketableSecuritiesTables</Role>
      <ShortName>Marketable Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/MarketableSecurities</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9954474 - Disclosure - Collaboration Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CollaborationAgreementsTables</Role>
      <ShortName>Collaboration Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/CollaborationAgreements</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9954475 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CommitmentsandContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/CommitmentsandContingencies</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9954476 - Disclosure - Stock-Based Awards (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/StockBasedAwardsTables</Role>
      <ShortName>Stock-Based Awards (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/StockBasedAwards</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9954477 - Disclosure - Net Income (Loss) Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/NetIncomeLossPerShareTables</Role>
      <ShortName>Net Income (Loss) Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/NetIncomeLossPerShare</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9954478 - Disclosure - Significant Accounting Policies - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/SignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Significant Accounting Policies - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9954479 - Disclosure - Fair Value Measurements - Schedule of Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/FairValueMeasurementsScheduleofAssetsandLiabilitiesDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9954480 - Disclosure - Marketable Securities - Summary of Available for Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/MarketableSecuritiesSummaryofAvailableforSaleSecuritiesDetails</Role>
      <ShortName>Marketable Securities - Summary of Available for Sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9954481 - Disclosure - Marketable Securities - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/MarketableSecuritiesNarrativeDetails</Role>
      <ShortName>Marketable Securities - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9954482 - Disclosure - Acquisition and Research Funding Collaboration Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/AcquisitionandResearchFundingCollaborationAgreementDetails</Role>
      <ShortName>Acquisition and Research Funding Collaboration Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/AcquisitionandResearchFundingCollaborationAgreement</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9954483 - Disclosure - Collaboration Agreements - Biogen (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CollaborationAgreementsBiogenDetails</Role>
      <ShortName>Collaboration Agreements - Biogen (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9954484 - Disclosure - Collaboration Agreements - Sanofi (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CollaborationAgreementsSanofiDetails</Role>
      <ShortName>Collaboration Agreements - Sanofi (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9954485 - Disclosure - Collaboration Agreements - Takeda (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CollaborationAgreementsTakedaDetails</Role>
      <ShortName>Collaboration Agreements - Takeda (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9954486 - Disclosure - Collaboration Agreements - Summary of Collaboration Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CollaborationAgreementsSummaryofCollaborationRevenueDetails</Role>
      <ShortName>Collaboration Agreements - Summary of Collaboration Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9954487 - Disclosure - Collaboration Agreements - Summary of Cost Sharing Payments and Reimbursements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CollaborationAgreementsSummaryofCostSharingPaymentsandReimbursementsDetails</Role>
      <ShortName>Collaboration Agreements - Summary of Cost Sharing Payments and Reimbursements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9954488 - Disclosure - Commitments and Contingencies - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CommitmentsandContingenciesNarrativeDetails</Role>
      <ShortName>Commitments and Contingencies - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9954489 - Disclosure - Commitments and Contingencies - Summary of Supplemental Lease Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CommitmentsandContingenciesSummaryofSupplementalLeaseInformationDetails</Role>
      <ShortName>Commitments and Contingencies - Summary of Supplemental Lease Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9954490 - Disclosure - Commitments and Contingencies - Summary of Company's Future Minimum Lease Commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CommitmentsandContingenciesSummaryofCompanysFutureMinimumLeaseCommitmentsDetails</Role>
      <ShortName>Commitments and Contingencies - Summary of Company's Future Minimum Lease Commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9954491 - Disclosure - Common Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/CommonStockDetails</Role>
      <ShortName>Common Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/CommonStock</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9954492 - Disclosure - Stock-Based Awards - Summary of Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/StockBasedAwardsSummaryofStockOptionActivityDetails</Role>
      <ShortName>Stock-Based Awards - Summary of Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9954493 - Disclosure - Stock-Based Awards - Summary of Assumptions Used for Estimating the Fair Value of Stock Options Granted (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/StockBasedAwardsSummaryofAssumptionsUsedforEstimatingtheFairValueofStockOptionsGrantedDetails</Role>
      <ShortName>Stock-Based Awards - Summary of Assumptions Used for Estimating the Fair Value of Stock Options Granted (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9954494 - Disclosure - Stock-Based Awards - Summary of Restricted Stock Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/StockBasedAwardsSummaryofRestrictedStockActivityDetails</Role>
      <ShortName>Stock-Based Awards - Summary of Restricted Stock Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9954495 - Disclosure - Stock-Based Awards - Summary of Stock-Based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/StockBasedAwardsSummaryofStockBasedCompensationExpenseDetails</Role>
      <ShortName>Stock-Based Awards - Summary of Stock-Based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9954496 - Disclosure - Net Income (Loss) Per Share - Calculation of Basic and Diluted Net Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/NetIncomeLossPerShareCalculationofBasicandDilutedNetLossDetails</Role>
      <ShortName>Net Income (Loss) Per Share - Calculation of Basic and Diluted Net Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/NetIncomeLossPerShareTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9954497 - Disclosure - Net Income (Loss) Per Share - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/NetIncomeLossPerShareNarrativeDetails</Role>
      <ShortName>Net Income (Loss) Per Share - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/NetIncomeLossPerShareTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="dnli-20240630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9954498 - Disclosure - Divestiture of Preclinical Small Molecule Programs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.denalitherapeutics.com/role/DivestitureofPreclinicalSmallMoleculeProgramsDetails</Role>
      <ShortName>Divestiture of Preclinical Small Molecule Programs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.denalitherapeutics.com/role/DivestitureofPreclinicalSmallMoleculePrograms</ParentRole>
      <Position>49</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-Q" isDefinitelyFs="true" isUsgaap="true" original="dnli-20240630.htm">dnli-20240630.htm</File>
    <File>dnli-20240630.xsd</File>
    <File>dnli-20240630_cal.xml</File>
    <File>dnli-20240630_def.xml</File>
    <File>dnli-20240630_lab.xml</File>
    <File>dnli-20240630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="595">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
