<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.10.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>154</ContextCount>
  <ElementCount>203</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>46</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Condensed Consolidated Statements of Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/CondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements of Changes in Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/CondensedConsolidatedStatementsOfChangesInEquity</Role>
      <ShortName>Condensed Consolidated Statements of Changes in Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/BasisOfPresentation</Role>
      <ShortName>Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Recent Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/RecentAccountingPronouncements</Role>
      <ShortName>Recent Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Revenue from Contracts with Customers</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/RevenueFromContractsWithCustomers</Role>
      <ShortName>Revenue from Contracts with Customers</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Fair Value of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/FairValueOfFinancialInstruments</Role>
      <ShortName>Fair Value of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Convertible Preferred Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ConvertiblePreferredStock</Role>
      <ShortName>Convertible Preferred Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Long-Term Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/LongTermDebt</Role>
      <ShortName>Long-Term Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/StockBasedCompensation</Role>
      <ShortName>Stock-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Components of Net Periodic Benefit Cost</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ComponentsOfNetPeriodicBenefitCost</Role>
      <ShortName>Components of Net Periodic Benefit Cost</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ComprehensiveIncomeLoss</Role>
      <ShortName>Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Litigation and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/LitigationAndContingencies</Role>
      <ShortName>Litigation and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Disposition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/Disposition</Role>
      <ShortName>Disposition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Impairment of Long-Lived Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ImpairmentOfLongLivedAssets</Role>
      <ShortName>Impairment of Long-Lived Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - Certain Relationships and Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/CertainRelationshipsAndRelatedPartyTransactions</Role>
      <ShortName>Certain Relationships and Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Basis of Presentation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/BasisOfPresentationPolicies</Role>
      <ShortName>Basis of Presentation (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/RecentAccountingPronouncements</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Revenue from Contracts with Customers (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/RevenueFromContractsWithCustomersTables</Role>
      <ShortName>Revenue from Contracts with Customers (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/RevenueFromContractsWithCustomers</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Components of Net Periodic Benefit Cost (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ComponentsOfNetPeriodicBenefitCostTables</Role>
      <ShortName>Components of Net Periodic Benefit Cost (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/ComponentsOfNetPeriodicBenefitCost</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/EarningsPerShare</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Comprehensive Income (Loss) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ComprehensiveIncomeLossTables</Role>
      <ShortName>Comprehensive Income (Loss) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/ComprehensiveIncomeLoss</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Disposition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/DispositionTables</Role>
      <ShortName>Disposition (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/Disposition</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - Basis of Presentation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/BasisOfPresentationDetails</Role>
      <ShortName>Basis of Presentation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/BasisOfPresentationPolicies</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Revenue from Contracts with Customers - Disaggregation of Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/RevenueFromContractsWithCustomersDisaggregationOfRevenueDetails</Role>
      <ShortName>Revenue from Contracts with Customers - Disaggregation of Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Revenue from Contracts with Customers - Future Performance Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/RevenueFromContractsWithCustomersFuturePerformanceObligationsDetails</Role>
      <ShortName>Revenue from Contracts with Customers - Future Performance Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2403404 - Disclosure - Revenue from Contracts with Customers - Contract Balances (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/RevenueFromContractsWithCustomersContractBalancesDetails</Role>
      <ShortName>Revenue from Contracts with Customers - Contract Balances (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2403405 - Disclosure - Revenue from Contracts with Customers - Cumulative Effect of Changes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/RevenueFromContractsWithCustomersCumulativeEffectOfChangesDetails</Role>
      <ShortName>Revenue from Contracts with Customers - Cumulative Effect of Changes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2405401 - Disclosure - Convertible Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ConvertiblePreferredStockDetails</Role>
      <ShortName>Convertible Preferred Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/ConvertiblePreferredStock</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2406401 - Disclosure - Long-Term Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/LongTermDebtDetails</Role>
      <ShortName>Long-Term Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/LongTermDebt</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2407401 - Disclosure - Stock-Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/StockBasedCompensationDetails</Role>
      <ShortName>Stock-Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/StockBasedCompensation</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Components of Net Periodic Benefit Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ComponentsOfNetPeriodicBenefitCostDetails</Role>
      <ShortName>Components of Net Periodic Benefit Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/ComponentsOfNetPeriodicBenefitCostTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2409401 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/IncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/IncomeTaxes</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/EarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/EarningsPerShareTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Comprehensive Income (Loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ComprehensiveIncomeLossDetails</Role>
      <ShortName>Comprehensive Income (Loss) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/ComprehensiveIncomeLossTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2413401 - Disclosure - Litigation and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/LitigationAndContingenciesDetails</Role>
      <ShortName>Litigation and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/LitigationAndContingencies</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Disposition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/DispositionDetails</Role>
      <ShortName>Disposition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/DispositionTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2415401 - Disclosure - Impairment of Long-Lived Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/ImpairmentOfLongLivedAssetsDetails</Role>
      <ShortName>Impairment of Long-Lived Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/ImpairmentOfLongLivedAssets</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="hhs-20180930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2416401 - Disclosure - Certain Relationships and Related Party Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.hartehanks.com/role/CertainRelationshipsAndRelatedPartyTransactionsDetails</Role>
      <ShortName>Certain Relationships and Related Party Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.hartehanks.com/role/CertainRelationshipsAndRelatedPartyTransactions</ParentRole>
      <Position>43</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>hhs-20180930.xml</File>
    <File>hhs-20180930.xsd</File>
    <File>hhs-20180930_cal.xml</File>
    <File>hhs-20180930_def.xml</File>
    <File>hhs-20180930_lab.xml</File>
    <File>hhs-20180930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2018-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/sic/2011-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2018-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2018-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/naics/2017-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
