<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.24.3</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>148</ContextCount>
  <ElementCount>250</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>46</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="qnst-20240930.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.quinstreet.com/20240930/taxonomy/role/Role_DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Condensed Consolidated Balance Sheets (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_StatementCondensedConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_StatementCondensedConsolidatedBalanceSheetsUnauditedParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100040 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100050 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossParentheticalUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100060 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfStockholdersEquityUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100070 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.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>8</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.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>9</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995455 - Disclosure - The Company</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureTheCompany</Role>
      <ShortName>The Company</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995465 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995475 - Disclosure - Revenue</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureRevenue</Role>
      <ShortName>Revenue</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995485 - Disclosure - Net Loss per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureNetLossPerShare</Role>
      <ShortName>Net Loss per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995495 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995505 - Disclosure - Acquisitions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureAcquisitions</Role>
      <ShortName>Acquisitions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995515 - Disclosure - Goodwill and Intangible Assets, Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsNet</Role>
      <ShortName>Goodwill and Intangible Assets, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995525 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995535 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureLeases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995545 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995565 - Disclosure - Stockholders' Equity and Stock Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureStockholdersEquityAndStockBenefitPlans</Role>
      <ShortName>Stockholders' Equity and Stock Benefit Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995575 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995585 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995595 - Disclosure - Revenue (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureRevenueTables</Role>
      <ShortName>Revenue (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureRevenue</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995605 - Disclosure - Net Loss per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureNetLossPerShareTables</Role>
      <ShortName>Net Loss per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureNetLossPerShare</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995615 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureFairValueMeasurements</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995625 - Disclosure - Acquisitions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureAcquisitionsTables</Role>
      <ShortName>Acquisitions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureAcquisitions</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995635 - Disclosure - Goodwill and Intangible Assets, Net (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsNetTables</Role>
      <ShortName>Goodwill and Intangible Assets, Net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsNet</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995645 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureLeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureLeases</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995655 - Disclosure - Stockholders' Equity and Stock Benefit Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureStockholdersEquityAndStockBenefitPlansTables</Role>
      <ShortName>Stockholders' Equity and Stock Benefit Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureStockholdersEquityAndStockBenefitPlans</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995665 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSegmentInformation</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995675 - Disclosure - Revenue - Schedule of Disaggregation of Net Revenue (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureRevenueScheduleOfDisaggregationOfNetRevenueDetail</Role>
      <ShortName>Revenue - Schedule of Disaggregation of Net Revenue (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995685 - Disclosure - Revenue - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureRevenueAdditionalInformationDetail</Role>
      <ShortName>Revenue - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995695 - Disclosure - Net Loss per Share - Calculation of Basic and Diluted Net Loss per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureNetLossPerShareCalculationOfBasicAndDilutedNetLossPerShareDetail</Role>
      <ShortName>Net Loss per Share - Calculation of Basic and Diluted Net Loss per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995705 - Disclosure - Fair Value Measurements - Schedule of Fair Value of Financial Instruments Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureFairValueMeasurementsScheduleOfFairValueOfFinancialInstrumentsMeasuredAtFairValueOnRecurringBasisDetail</Role>
      <ShortName>Fair Value Measurements - Schedule of Fair Value of Financial Instruments Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995715 - Disclosure - Fair Value Measurements - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureFairValueMeasurementsAdditionalInformationDetail</Role>
      <ShortName>Fair Value Measurements - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995725 - Disclosure - Fair Value Measurements - Schedule of Change in Contingent Consideration (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureFairValueMeasurementsScheduleOfChangeInContingentConsiderationDetail</Role>
      <ShortName>Fair Value Measurements - Schedule of Change in Contingent Consideration (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995735 - Disclosure - Acquisitions - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureAcquisitionsAdditionalInformationDetail</Role>
      <ShortName>Acquisitions - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995745 - Disclosure - Acquisitions - Schedule of Consideration (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureAcquisitionsScheduleOfConsiderationDetail</Role>
      <ShortName>Acquisitions - Schedule of Consideration (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995755 - Disclosure - Acquisitions - Schedule of Consideration (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureAcquisitionsScheduleOfConsiderationParentheticalDetail</Role>
      <ShortName>Acquisitions - Schedule of Consideration (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995765 - Disclosure - Acquisitions - Schedule of Components and Preliminary Allocation of Purchase Price, Fair Values and Estimated Useful Lives of Identifiable Assets Acquired (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureAcquisitionsScheduleOfComponentsAndPreliminaryAllocationOfPurchasePriceFairValuesAndEstimatedUsefulLivesOfIdentifiableAssetsAcqu</Role>
      <ShortName>Acquisitions - Schedule of Components and Preliminary Allocation of Purchase Price, Fair Values and Estimated Useful Lives of Identifiable Assets Acquired (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995775 - Disclosure - Goodwill and Intangible Assets, Net - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsNetAdditionalInformationDetail</Role>
      <ShortName>Goodwill and Intangible Assets, Net - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995795 - Disclosure - Goodwill and Intangible Assets, Net - Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsNetIntangibleAssetsDetail</Role>
      <ShortName>Goodwill and Intangible Assets, Net - Intangible Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995805 - Disclosure - Goodwill and Intangible Assets, Net - Amortization Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsNetAmortizationExpenseDetail</Role>
      <ShortName>Goodwill and Intangible Assets, Net - Amortization Expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995815 - Disclosure - Income Taxes - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureIncomeTaxesAdditionalInformationDetail</Role>
      <ShortName>Income Taxes - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995825 - Disclosure - Leases - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureLeasesAdditionalInformationDetail</Role>
      <ShortName>Leases - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995835 - Disclosure - Leases - Components of Lease Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureLeasesComponentsOfLeaseExpenseDetail</Role>
      <ShortName>Leases - Components of Lease Expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>995855 - Disclosure - Leases - Supplemental Information Related to Operating Leases (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureLeasesSupplementalInformationRelatedToOperatingLeasesDetail</Role>
      <ShortName>Leases - Supplemental Information Related to Operating Leases (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>995865 - Disclosure - Leases - Maturities of Operating Lease Liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureLeasesMaturitiesOfOperatingLeaseLiabilitiesDetail</Role>
      <ShortName>Leases - Maturities of Operating Lease Liabilities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>995875 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetail</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>995885 - Disclosure - Stockholders' Equity and Stock Benefit Plans - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureStockholdersEquityAndStockBenefitPlansAdditionalInformationDetail</Role>
      <ShortName>Stockholders' Equity and Stock Benefit Plans - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>995895 - Disclosure - Stockholders' Equity and Stock Benefit Plans - Summary of Stock-based Compensation Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureStockholdersEquityAndStockBenefitPlansSummaryOfStockbasedCompensationExpenseDetail</Role>
      <ShortName>Stockholders' Equity and Stock Benefit Plans - Summary of Stock-based Compensation Expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>995905 - Disclosure - Stockholders' Equity and Stock Benefit Plans - Schedule of RSU Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/DisclosureStockholdersEquityAndStockBenefitPlansScheduleOfRsuActivityDetail</Role>
      <ShortName>Stockholders' Equity and Stock Benefit Plans - Schedule of RSU Activity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>995915 - Disclosure - Segment Information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSegmentInformationAdditionalInformationDetail</Role>
      <ShortName>Segment Information - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="qnst-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>995925 - Disclosure - Segment Information - Net Revenue and Long-Lived Assets by Geographic Area (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.quinstreet.com/20240930/taxonomy/role/Role_DisclosureSegmentInformationNetRevenueAndLongLivedAssetsByGeographicAreaDetail</Role>
      <ShortName>Segment Information - Net Revenue and Long-Lived Assets by Geographic Area (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</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="qnst-20240930.htm">qnst-20240930.htm</File>
    <File>qnst-20240930.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2024</BaseTaxonomy>
    <BaseTaxonomy items="484">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
