<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.20.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>188</ContextCount>
  <ElementCount>278</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>56</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/StatementCondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100030 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100040 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Deficit)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/StatementCondensedConsolidatedStatementsOfStockholdersEquityDeficit</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Deficit)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100050 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100060 - Disclosure - Organization and Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureOrganizationAndAccountingPronouncements</Role>
      <ShortName>Organization and Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100070 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Fair Value of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstruments</Role>
      <ShortName>Fair Value of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Certain Financial Statement Caption Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCertainFinancialStatementCaptionInformation</Role>
      <ShortName>Certain Financial Statement Caption Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Notes Payable</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureNotesPayable</Role>
      <ShortName>Notes Payable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100110 - Disclosure - Collaboration and License Agreement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCollaborationAndLicenseAgreement</Role>
      <ShortName>Collaboration and License Agreement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://equilliumbio.com/20200930/taxonomy/role/DisclosureOrganizationAndAccountingPronouncements</ParentRole>
      <Position>14</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://equilliumbio.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>15</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Fair Value of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsTables</Role>
      <ShortName>Fair Value of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://equilliumbio.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstruments</ParentRole>
      <Position>16</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Certain Financial Statement Caption Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCertainFinancialStatementCaptionInformationTables</Role>
      <ShortName>Certain Financial Statement Caption Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCertainFinancialStatementCaptionInformation</ParentRole>
      <Position>17</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100170 - Disclosure - Notes Payable (Tables)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureNotesPayableTables</Role>
      <ShortName>Notes Payable (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://equilliumbio.com/20200930/taxonomy/role/DisclosureNotesPayable</ParentRole>
      <Position>18</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100180 - Disclosure - Stockholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquityTables</Role>
      <ShortName>Stockholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquity</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100190 - Disclosure - Organization and Accounting Pronouncements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureOrganizationAndAccountingPronouncementsAdditionalInformationDetails</Role>
      <ShortName>Organization and Accounting Pronouncements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Summary of Significant Accounting Policies - Summary of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesSummaryOfPotentiallyDilutiveSecuritiesNotIncludedInCalculationOfDilutedNetLossPerShareDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Summary of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Fair Value of Financial Instruments - Summary of Assets that Require Fair Value Measurements on Recurring Basis and Their Respective Input Levels Based on Fair Value Hierarchy (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsSummaryOfAssetsThatRequireFairValueMeasurementsOnRecurringBasisAndTheirRespectiveInputLevelsBasedOnFairValueHierarchyDetails</Role>
      <ShortName>Fair Value of Financial Instruments - Summary of Assets that Require Fair Value Measurements on Recurring Basis and Their Respective Input Levels Based on Fair Value Hierarchy (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100230 - Disclosure - Fair Value of Financial Instruments - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsAdditionalInformationDetails</Role>
      <ShortName>Fair Value of Financial Instruments - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100240 - Disclosure - Certain Financial Statement Caption Information - Schedule of Company's Short-Term Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCertainFinancialStatementCaptionInformationScheduleOfCompanySShortTermInvestmentsDetails</Role>
      <ShortName>Certain Financial Statement Caption Information - Schedule of Company's Short-Term Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Certain Financial Statement Caption Information - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCertainFinancialStatementCaptionInformationAdditionalInformationDetails</Role>
      <ShortName>Certain Financial Statement Caption Information - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100260 - Disclosure - Certain Financial Statement Caption Information - Schedule of Accrued Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCertainFinancialStatementCaptionInformationScheduleOfAccruedExpensesDetails</Role>
      <ShortName>Certain Financial Statement Caption Information - Schedule of Accrued Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100270 - Disclosure - Notes Payable - Additional Information (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureNotesPayableAdditionalInformationDetails</Role>
      <ShortName>Notes Payable - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Notes Payable - Schedule of Aggregate Carrying Amounts of Term Loans (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureNotesPayableScheduleOfAggregateCarryingAmountsOfTermLoansDetails</Role>
      <ShortName>Notes Payable - Schedule of Aggregate Carrying Amounts of Term Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Notes Payable - Schedule Future Maturities of Term Loans, Including Final Payment Fee (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureNotesPayableScheduleFutureMaturitiesOfTermLoansIncludingFinalPaymentFeeDetails</Role>
      <ShortName>Notes Payable - Schedule Future Maturities of Term Loans, Including Final Payment Fee (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Collaboration And License Agreements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureCollaborationAndLicenseAgreementsAdditionalInformationDetails</Role>
      <ShortName>Collaboration And License Agreements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Stockholders' Equity - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetails</Role>
      <ShortName>Stockholders' Equity - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100330 - Disclosure - Stockholders' Equity - Summary of Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetails</Role>
      <ShortName>Stockholders' Equity - Summary of Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100340 - Disclosure - Stockholders' Equity - Summary of Stock Option Activity (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityParentheticalDetails</Role>
      <ShortName>Stockholders' Equity - Summary of Stock Option Activity (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100350 - Disclosure - Stockholders' Equity - Summary of Non-cash Stock-based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquitySummaryOfNonCashStockBasedCompensationExpenseDetails</Role>
      <ShortName>Stockholders' Equity - Summary of Non-cash Stock-based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="eq-20200930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://equilliumbio.com/20200930/taxonomy/role/DisclosureStockholdersEquitySummaryOfCommonStockReservedForFutureIssuanceDetails</Role>
      <ShortName>Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>eq-20200930.xml</File>
    <File>eq-20200930.xsd</File>
    <File>eq-20200930_cal.xml</File>
    <File>eq-20200930_def.xml</File>
    <File>eq-20200930_lab.xml</File>
    <File>eq-20200930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
