<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.2.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>222</ContextCount>
  <ElementCount>329</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>51</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="posh-20220630.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://poshmark.com/20220630/taxonomy/role/Role_StatementCondensedConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100030 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_StatementCondensedConsolidatedBalanceSheetsParentheticalUnaudited</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100040 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfOperationsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100050 - Statement - Condensed Consolidated Statements of Comprehensive Loss (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/StatementCondensedConsolidatedStatementsOfComprehensiveLossUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Loss (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100060 - Statement - Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' (Deficit) Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfRedeemableConvertiblePreferredStockAndStockholdersDeficitEquityUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' (Deficit) Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="posh-20220630.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://poshmark.com/20220630/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Organization</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureOrganization</Role>
      <ShortName>Organization</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Revision of Prior Periods' Financial Statement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureRevisionOfPriorPeriodsFinancialStatement3</Role>
      <ShortName>Revision of Prior Periods' Financial Statement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100110 - Disclosure - Supplemental Financial Statement Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSupplementalFinancialStatementInformation</Role>
      <ShortName>Supplemental Financial Statement Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Business Combination</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureBusinessCombination</Role>
      <ShortName>Business Combination</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Goodwill and Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureGoodwillAndIntangibleAssets</Role>
      <ShortName>Goodwill and Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureLeases1</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Common Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommonStock</Role>
      <ShortName>Common Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Stock-based Compensation Plan</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlan</Role>
      <ShortName>Stock-based Compensation Plan</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Net Loss Per Share Attributable to Common Stockholders</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholders1</Role>
      <ShortName>Net Loss Per Share Attributable to Common Stockholders</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100230 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100240 - Disclosure - Subsequent Event</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureSubsequentEvent1</Role>
      <ShortName>Subsequent Event</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100260 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100270 - Disclosure - Revision of Prior Periods' Financial Statement (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureRevisionOfPriorPeriodsFinancialStatementTables</Role>
      <ShortName>Revision of Prior Periods' Financial Statement (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/DisclosureRevisionOfPriorPeriodsFinancialStatement3</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Supplemental Financial Statement Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSupplementalFinancialStatementInformationTables</Role>
      <ShortName>Supplemental Financial Statement Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSupplementalFinancialStatementInformation</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureFairValueMeasurements</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100300 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Business Combination (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureBusinessCombinationTables</Role>
      <ShortName>Business Combination (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/DisclosureBusinessCombination</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Goodwill and Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsTables</Role>
      <ShortName>Goodwill and Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/DisclosureGoodwillAndIntangibleAssets</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100330 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureLeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/DisclosureLeases1</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Common Stock (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommonStockTables</Role>
      <ShortName>Common Stock (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommonStock</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100370 - Disclosure - Stock-based Compensation Plan (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlanTables</Role>
      <ShortName>Stock-based Compensation Plan (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlan</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100380 - Disclosure - Net Loss Per Share Attributable to Common Stockholders (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholdersTables</Role>
      <ShortName>Net Loss Per Share Attributable to Common Stockholders (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholders1</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100390 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureIncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureIncomeTaxes</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100400 - Disclosure - Organization - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureOrganizationAdditionalInformationDetails</Role>
      <ShortName>Organization - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100410 - Disclosure - Summary of Significant Accounting Policies - Summary of Referral Incentives, Joint Incentives, Refunds and Buyer Incentives Recorded in Consolidated Statements of Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesSummaryOfReferralIncentivesJointIncentivesRefundsAndBuyerIncentivesRecordedInConsolidatedStatementsOfOperationsDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Summary of Referral Incentives, Joint Incentives, Refunds and Buyer Incentives Recorded in Consolidated Statements of Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>100420 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>100430 - Disclosure - Revision of Prior Periods' Financial Statement - Summary of Effect of Correction of Misstatements and Resulting Revision - Condensed Consolidated Statements of Operations and Comprehensive Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureRevisionOfPriorPeriodsFinancialStatementSummaryOfEffectOfCorrectionOfMisstatementsAndResultingRevisionCondensedConsolidatedState</Role>
      <ShortName>Revision of Prior Periods' Financial Statement - Summary of Effect of Correction of Misstatements and Resulting Revision - Condensed Consolidated Statements of Operations and Comprehensive Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>100440 - Disclosure - Revision of Prior Periods' Financial Statement - Summary of Effect of Correction of Misstatements and Resulting Revision - Condensed Consolidated Statements of Changes in Stockholders' (Deficit) Equity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureRevisionOfPriorPeriodsFinancialStatementSummaryOfEffectOfCorrectionOfMisstatementsAndResultingRevisionCondensedConsolidatedState1</Role>
      <ShortName>Revision of Prior Periods' Financial Statement - Summary of Effect of Correction of Misstatements and Resulting Revision - Condensed Consolidated Statements of Changes in Stockholders' (Deficit) Equity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>100450 - Disclosure - Revision of Prior Periods' Financial Statement - Summary of Effect of Correction of Misstatements and Resulting Revision - Condensed Consolidated Statements of Cash Flows (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureRevisionOfPriorPeriodsFinancialStatementSummaryOfEffectOfCorrectionOfMisstatementsAndResultingRevisionCondensedConsolidatedState2</Role>
      <ShortName>Revision of Prior Periods' Financial Statement - Summary of Effect of Correction of Misstatements and Resulting Revision - Condensed Consolidated Statements of Cash Flows (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>100460 - Disclosure - Supplemental Financial Statement Information - Schedule of Fair Value of Cash Equivalents (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureSupplementalFinancialStatementInformationScheduleOfFairValueOfCashEquivalentsDetails</Role>
      <ShortName>Supplemental Financial Statement Information - Schedule of Fair Value of Cash Equivalents (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>100470 - Disclosure - Supplemental Financial Statement Information - Schedule of Property and Equipment, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSupplementalFinancialStatementInformationScheduleOfPropertyAndEquipmentNetDetails</Role>
      <ShortName>Supplemental Financial Statement Information - Schedule of Property and Equipment, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>100480 - Disclosure - Supplemental Financial Statement Information - Schedule of Accrued Expenses and Other Current Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureSupplementalFinancialStatementInformationScheduleOfAccruedExpensesAndOtherCurrentLiabilitiesDetails</Role>
      <ShortName>Supplemental Financial Statement Information - Schedule of Accrued Expenses and Other Current Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>100490 - Disclosure - Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureFairValueMeasurementsScheduleOfFinancialInstrumentsMeasuredAtFairValueDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>100500 - Disclosure - Fair Value Measurements - Schedule of Change in Contingent Consideration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureFairValueMeasurementsScheduleOfChangeInContingentConsiderationDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Change in Contingent Consideration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>100510 - Disclosure - Fair Value Measurements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureFairValueMeasurementsAdditionalInformationDetails</Role>
      <ShortName>Fair Value Measurements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>100520 - Disclosure - Commitments and Contingencies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>100530 - Disclosure - Business Combination - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureBusinessCombinationAdditionalInformationDetails</Role>
      <ShortName>Business Combination - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>100540 - Disclosure - Business Combination - Summary of Allocation of Purchase Price of Assets Acquired and Liabilities Assumed (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureBusinessCombinationSummaryOfAllocationOfPurchasePriceOfAssetsAcquiredAndLiabilitiesAssumedDetails</Role>
      <ShortName>Business Combination - Summary of Allocation of Purchase Price of Assets Acquired and Liabilities Assumed (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>100550 - Disclosure - Goodwill and Intangible Assets - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsAdditionalInformationDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>100560 - Disclosure - Goodwill and Intangible Assets - Summary of Carrying Value of Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfCarryingValueOfIntangibleAssetsDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Summary of Carrying Value of Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>100570 - Disclosure - Goodwill and Intangible Assets - Summary of Future Amortization Expense of Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfFutureAmortizationExpenseOfIntangibleAssetsDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Summary of Future Amortization Expense of Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>100580 - Disclosure - Leases - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureLeasesAdditionalInformationDetails</Role>
      <ShortName>Leases - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>100590 - Disclosure - Leases - Schedule of Components of Operating Lease Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureLeasesScheduleOfComponentsOfOperatingLeaseExpenseDetails</Role>
      <ShortName>Leases - Schedule of Components of Operating Lease Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>100600 - Disclosure - Leases - Schedule of Supplemental Cash Flow Information Related to Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureLeasesScheduleOfSupplementalCashFlowInformationRelatedToLeasesDetails</Role>
      <ShortName>Leases - Schedule of Supplemental Cash Flow Information Related to Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>100610 - Disclosure - Leases - Schedule of Future Minimum Lease Payments Under Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureLeasesScheduleOfFutureMinimumLeasePaymentsUnderOperatingLeasesDetails</Role>
      <ShortName>Leases - Schedule of Future Minimum Lease Payments Under Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>100620 - Disclosure - Leases - Schedule of Future Minimum Payments For Noncancellable Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureLeasesScheduleOfFutureMinimumPaymentsForNoncancellableOperatingLeasesDetails</Role>
      <ShortName>Leases - Schedule of Future Minimum Payments For Noncancellable Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>100630 - Disclosure - Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureRedeemableConvertiblePreferredStockSummaryOfRedeemableConvertiblePreferredStockDetails</Role>
      <ShortName>Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>100670 - Disclosure - Convertible Notes - Additional Information (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureConvertibleNotesAdditionalInformationDetails</Role>
      <ShortName>Convertible Notes - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>100680 - Disclosure - Common Stock - Summary of Common Stock Reserved for Future Issuance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureCommonStockSummaryOfCommonStockReservedForFutureIssuanceDetails</Role>
      <ShortName>Common Stock - Summary of Common Stock Reserved for Future Issuance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>100690 - Disclosure - Stock-based Compensation Plan - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlanAdditionalInformationDetails</Role>
      <ShortName>Stock-based Compensation Plan - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>100700 - Disclosure - Stock-based Compensation Plan - Schedule of Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlanScheduleOfOptionActivityDetails</Role>
      <ShortName>Stock-based Compensation Plan - Schedule of Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>100710 - Disclosure - Stock-based Compensation Plan - Schedule of RSUs Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlanScheduleOfRsusActivityDetails</Role>
      <ShortName>Stock-based Compensation Plan - Schedule of RSUs Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>100720 - Disclosure - Stock-based Compensation Plan - Schedule of Assumptions to Value Stock Options Granted (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlanScheduleOfAssumptionsToValueStockOptionsGrantedDetails</Role>
      <ShortName>Stock-based Compensation Plan - Schedule of Assumptions to Value Stock Options Granted (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>100730 - Disclosure - Stock-based Compensation Plan - Schedule of Allocated Stock-based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationPlanScheduleOfAllocatedStockBasedCompensationExpenseDetails</Role>
      <ShortName>Stock-based Compensation Plan - Schedule of Allocated Stock-based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>100740 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Summary of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholdersSummaryOfBasicAndDilutedNetLossPerShareAttributableToCommonStockholdersDetails</Role>
      <ShortName>Net Loss Per Share Attributable to Common Stockholders - Summary of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>100760 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Schedule of Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholdersScheduleOfPotentiallyDilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPe</Role>
      <ShortName>Net Loss Per Share Attributable to Common Stockholders - Schedule of Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>100770 - Disclosure - Income Taxes - Summary of Effective Tax Rate from Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/Role_DisclosureIncomeTaxesSummaryOfEffectiveTaxRateFromLossDetails</Role>
      <ShortName>Income Taxes - Summary of Effective Tax Rate from Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="posh-20220630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>100780 - Disclosure - Subsequent Event - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://poshmark.com/20220630/taxonomy/role/DisclosureSubsequentEventAdditionalInformationDetails</Role>
      <ShortName>Subsequent Event - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[dq-0542-Deprecated-Concept] Concept EarningsPerShareBasicAndDiluted in us-gaap/2021 used in 14 facts was deprecated in us-gaap/2022 as of 2022 and should not be used. posh-20220630.htm 1120, 1124, 1128, 1132, 3769, 3773, 3777, 3955, 3959, 3963, 6273, 6277, 6281, 6285</Log>
    <Log type="Warning">[dq-0542-Deprecated-Concept] Concept WeightedAverageNumberOfShareOutstandingBasicAndDiluted in us-gaap/2021 used in 8 facts was deprecated in us-gaap/2022 as of 2022 and should not be used. posh-20220630.htm 1139, 1143, 1147, 1151, 6254, 6258, 6262, 6266</Log>
    <Log type="Warning">[dq-0542-Deprecated-Concept] Concept FairValueAssetsLevel1ToLevel2TransfersAmount in us-gaap/2021 used in 2 facts was deprecated in us-gaap/2022 as of 2022 and should not be used. posh-20220630.htm 5065</Log>
    <Log type="Warning">[dq-0542-Deprecated-Concept] Concept FairValueAssetsLevel2ToLevel1TransfersAmount in us-gaap/2021 used in 2 facts was deprecated in us-gaap/2022 as of 2022 and should not be used. posh-20220630.htm 5065</Log>
    <Log type="Warning">[dq-0542-Deprecated-Concept] Concept FairValueLiabilitiesLevel1ToLevel2TransfersAmount in us-gaap/2021 used in 2 facts was deprecated in us-gaap/2022 as of 2022 and should not be used. posh-20220630.htm 5065</Log>
    <Log type="Warning">[dq-0542-Deprecated-Concept] Concept FairValueLiabilitiesLevel2ToLevel1TransfersAmount in us-gaap/2021 used in 2 facts was deprecated in us-gaap/2022 as of 2022 and should not be used. posh-20220630.htm 5065</Log>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 1 fact(s) appearing in ix:hidden were eligible for transformation: us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1 -  posh-20220630.htm 8</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="posh-20220630.htm">posh-20220630.htm</File>
    <File>posh-20220630.xsd</File>
    <File>posh-20220630_cal.xml</File>
    <File>posh-20220630_def.xml</File>
    <File>posh-20220630_lab.xml</File>
    <File>posh-20220630_pre.xml</File>
    <File>posh-ex10_1.htm</File>
    <File>posh-ex31_1.htm</File>
    <File>posh-ex31_2.htm</File>
    <File>posh-ex32_1.htm</File>
    <File>posh-ex32_2.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>img222476794_0.jpg</File>
    <File>img222476794_1.jpg</File>
    <File>img222476794_2.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy items="972">http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy items="32">http://xbrl.sec.gov/dei/2021q4</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
