<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.10.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>278</ContextCount>
  <ElementCount>236</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>71</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Consolidated Condensed Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/StatementConsolidatedCondensedBalanceSheets</Role>
      <ShortName>Consolidated Condensed Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Consolidated Condensed Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/StatementConsolidatedCondensedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Condensed Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100030 - Statement - Consolidated Condensed Statements of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/StatementConsolidatedCondensedStatementsOfIncome</Role>
      <ShortName>Consolidated Condensed Statements of Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100040 - Statement - Consolidated Condensed Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/StatementConsolidatedCondensedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Condensed Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100050 - Statement - Consolidated Condensed Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/StatementConsolidatedCondensedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Condensed Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100060 - Disclosure - The Company and Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureTheCompanyAndSubsequentEvents</Role>
      <ShortName>The Company and Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100070 - Disclosure - Basis of Presentation and New Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureBasisOfPresentationAndNewAccountingPronouncements</Role>
      <ShortName>Basis of Presentation and New Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Etratech Acquisition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisition</Role>
      <ShortName>Etratech Acquisition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100110 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDebt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Derivative Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDerivativeFinancialInstruments</Role>
      <ShortName>Derivative Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Fair Value Measurement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureFairValueMeasurement</Role>
      <ShortName>Fair Value Measurement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Reclassifications Out of Accumulated Other Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>Reclassifications Out of Accumulated Other Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Unearned Revenue</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureUnearnedRevenue</Role>
      <ShortName>Unearned Revenue</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Basis of Presentation and New Accounting Pronouncements (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureBasisOfPresentationAndNewAccountingPronouncementsPolicies</Role>
      <ShortName>Basis of Presentation and New Accounting Pronouncements (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureBasisOfPresentationAndNewAccountingPronouncements</ParentRole>
      <Position>17</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100170 - Disclosure - The Company and Subsequent Events (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureTheCompanyAndSubsequentEventsTables</Role>
      <ShortName>The Company and Subsequent Events (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureTheCompanyAndSubsequentEvents</ParentRole>
      <Position>18</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100180 - Disclosure - Basis of Presentation and New Accounting Pronouncements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureBasisOfPresentationAndNewAccountingPronouncementsTables</Role>
      <ShortName>Basis of Presentation and New Accounting Pronouncements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureBasisOfPresentationAndNewAccountingPronouncements</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100190 - Disclosure - Etratech Acquisition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionTables</Role>
      <ShortName>Etratech Acquisition (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisition</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEarningsPerShare</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Segment Reporting (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSegmentReportingTables</Role>
      <ShortName>Segment Reporting (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSegmentReporting</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDebt</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100230 - Disclosure - Derivative Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDerivativeFinancialInstrumentsTables</Role>
      <ShortName>Derivative Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDerivativeFinancialInstruments</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100240 - Disclosure - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveIncomeLoss</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Unearned Revenue (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureUnearnedRevenueTables</Role>
      <ShortName>Unearned Revenue (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureUnearnedRevenue</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100260 - Disclosure - The Company and Subsequent Events - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureTheCompanyAndSubsequentEventsAdditionalInformationDetail</Role>
      <ShortName>The Company and Subsequent Events - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100270 - Disclosure - The Company and Subsequent Events - Summary of Reconciliation of Beginning and Ending Restructuring Liability (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureTheCompanyAndSubsequentEventsSummaryOfReconciliationOfBeginningAndEndingRestructuringLiabilityDetail</Role>
      <ShortName>The Company and Subsequent Events - Summary of Reconciliation of Beginning and Ending Restructuring Liability (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Basis of Presentation and New Accounting Pronouncements (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureBasisOfPresentationAndNewAccountingPronouncementsDetail</Role>
      <ShortName>Basis of Presentation and New Accounting Pronouncements (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureBasisOfPresentationAndNewAccountingPronouncementsTables</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Summary of Activity in Allowance for Doubtful Accounts (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSummaryOfActivityInAllowanceForDoubtfulAccountsDetail</Role>
      <ShortName>Summary of Activity in Allowance for Doubtful Accounts (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100300 - Disclosure - Summary of Financial Statement Affected by Application of ASU 2014-09 and Related Amendments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSummaryOfFinancialStatementAffectedByApplicationOfASU201409AndRelatedAmendmentsDetail</Role>
      <ShortName>Summary of Financial Statement Affected by Application of ASU 2014-09 and Related Amendments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Etratech Acquisition - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionAdditionalInformationDetail</Role>
      <ShortName>Etratech Acquisition - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Etratech Acquisition - Summary of Preliminary Allocation (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionSummaryOfPreliminaryAllocationDetail</Role>
      <ShortName>Etratech Acquisition - Summary of Preliminary Allocation (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100330 - Disclosure - Etratech Acquisition - Supplemental Pro Forma Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionSupplementalProFormaInformationDetail</Role>
      <ShortName>Etratech Acquisition - Supplemental Pro Forma Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100340 - Disclosure - Etratech Acquisition - Schedule of Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionScheduleOfIntangibleAssetsDetail</Role>
      <ShortName>Etratech Acquisition - Schedule of Intangible Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100350 - Disclosure - Etratech Acquisition - Summary of Amortization Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionSummaryOfAmortizationExpenseDetail</Role>
      <ShortName>Etratech Acquisition - Summary of Amortization Expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Etratech Acquisition - Summary of Amortization Expense for Prospective Years (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionSummaryOfAmortizationExpenseForProspectiveYearsDetail</Role>
      <ShortName>Etratech Acquisition - Summary of Amortization Expense for Prospective Years (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>100370 - Disclosure - Etratech Acquisition - Summary of Property and Equipment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEtratechAcquisitionSummaryOfPropertyAndEquipmentDetail</Role>
      <ShortName>Etratech Acquisition - Summary of Property and Equipment (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>100380 - Disclosure - Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEarningsPerShareDetail</Role>
      <ShortName>Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureEarningsPerShareTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>100390 - Disclosure - Segment Reporting - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSegmentReportingAdditionalInformationDetail</Role>
      <ShortName>Segment Reporting - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>100400 - Disclosure - Segment Information about Reported Product Revenues, Depreciation and Amortization and Operating Income (Loss) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSegmentInformationAboutReportedProductRevenuesDepreciationAndAmortizationAndOperatingIncomeLossDetail</Role>
      <ShortName>Segment Information about Reported Product Revenues, Depreciation and Amortization and Operating Income (Loss) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>100410 - Disclosure - Segment Reporting (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSegmentReportingDetail</Role>
      <ShortName>Segment Reporting (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSegmentReportingTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>100420 - Disclosure - Debt - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDebtAdditionalInformationDetail</Role>
      <ShortName>Debt - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>100430 - Disclosure - Summary of Company's Debt (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureSummaryOfCompanySDebtDetail</Role>
      <ShortName>Summary of Company's Debt (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>100440 - Disclosure - Principal Maturities of Debt (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosurePrincipalMaturitiesOfDebtDetail</Role>
      <ShortName>Principal Maturities of Debt (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>100450 - Disclosure - Derivative Financial Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureDerivativeFinancialInstrumentsAdditionalInformationDetail</Role>
      <ShortName>Derivative Financial Instruments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>100460 - Disclosure - Information Related to Recurring Fair Value Measurement of Derivative Instruments in Our Consolidated Condensed Balance Sheet (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureInformationRelatedToRecurringFairValueMeasurementOfDerivativeInstrumentsInOurConsolidatedCondensedBalanceSheetDetail</Role>
      <ShortName>Information Related to Recurring Fair Value Measurement of Derivative Instruments in Our Consolidated Condensed Balance Sheet (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>100470 - Disclosure - Information Related to Effect of Derivative Instruments on Our Consolidated Condensed Statements of Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureInformationRelatedToEffectOfDerivativeInstrumentsOnOurConsolidatedCondensedStatementsOfIncomeDetail</Role>
      <ShortName>Information Related to Effect of Derivative Instruments on Our Consolidated Condensed Statements of Income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>100480 - Disclosure - Fair Value Measurement - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureFairValueMeasurementAdditionalInformationDetail</Role>
      <ShortName>Fair Value Measurement - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>100490 - Disclosure - Schedule of Reclassification Adjustments and Other Activities Impacting Accumulated Other Comprehensive Income (Loss) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureScheduleOfReclassificationAdjustmentsAndOtherActivitiesImpactingAccumulatedOtherComprehensiveIncomeLossDetail</Role>
      <ShortName>Schedule of Reclassification Adjustments and Other Activities Impacting Accumulated Other Comprehensive Income (Loss) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>100500 - Disclosure - Unearned Revenue By Segment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureUnearnedRevenueBySegmentDetail</Role>
      <ShortName>Unearned Revenue By Segment (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="thrm-20180630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>100510 - Disclosure - Changes in Unearned Revenue (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.gentherm.com/20180630/taxonomy/role/DisclosureChangesInUnearnedRevenueDetail</Role>
      <ShortName>Changes in Unearned Revenue (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>thrm-20180630.xml</File>
    <File>thrm-20180630.xsd</File>
    <File>thrm-20180630_cal.xml</File>
    <File>thrm-20180630_def.xml</File>
    <File>thrm-20180630_lab.xml</File>
    <File>thrm-20180630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.sec.gov/country/2017-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2017-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2014-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/invest/2013-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
