<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.21.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>245</ContextCount>
  <ElementCount>365</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>89</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001002 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002003 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1003004 - Statement - Condensed Consolidated Statements of Operations (unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CondensedConsolidatedStatementsofOperationsunaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations (unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004005 - Statement - Condensed Consolidated Statements of Comprehensive Loss (unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CondensedConsolidatedStatementsofComprehensiveLossunaudited</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Loss (unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1005006 - Statement - Condensed Consolidated Statements of Changes in Stockholders??? Deficit (unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CondensedConsolidatedStatementsofChangesinStockholdersDeficitunaudited</Role>
      <ShortName>Condensed Consolidated Statements of Changes in Stockholders??? Deficit (unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1007008 - Statement - Condensed Consolidated Statements of Cash Flows (unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CondensedConsolidatedStatementsofCashFlowsunaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2101101 - Disclosure - Business and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/BusinessandBasisofPresentation</Role>
      <ShortName>Business and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2104102 - Disclosure - Nexperia Arrangement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/NexperiaArrangement</Role>
      <ShortName>Nexperia Arrangement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2106103 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2112104 - Disclosure - Concentration of Credit Risk and Significant Customers</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/ConcentrationofCreditRiskandSignificantCustomers</Role>
      <ShortName>Concentration of Credit Risk and Significant Customers</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2115105 - Disclosure - Inventory</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/Inventory</Role>
      <ShortName>Inventory</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2118106 - Disclosure - Debts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/Debts</Role>
      <ShortName>Debts</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2123107 - Disclosure - Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW")</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSW</Role>
      <ShortName>Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW")</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2128108 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CommitmentsandContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2132109 - Disclosure - Stockholders' Deficit</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockholdersDeficit</Role>
      <ShortName>Stockholders' Deficit</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2137110 - Disclosure - Stock Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockBasedCompensation</Role>
      <ShortName>Stock Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2144111 - Disclosure - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/RelatedPartyTransactions</Role>
      <ShortName>Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2146112 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/SubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2202201 - Disclosure - Business and Basis of Presentation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/BusinessandBasisofPresentationPolicies</Role>
      <ShortName>Business and Basis of Presentation (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://transphormusa.com/role/FairValueMeasurements</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2313302 - Disclosure - Concentration of Credit Risk and Significant Customers (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/ConcentrationofCreditRiskandSignificantCustomersTables</Role>
      <ShortName>Concentration of Credit Risk and Significant Customers (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://transphormusa.com/role/ConcentrationofCreditRiskandSignificantCustomers</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2316303 - Disclosure - Inventory (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/InventoryTables</Role>
      <ShortName>Inventory (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://transphormusa.com/role/Inventory</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2319304 - Disclosure - Debts (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/DebtsTables</Role>
      <ShortName>Debts (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://transphormusa.com/role/Debts</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2324305 - Disclosure - Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSWTables</Role>
      <ShortName>Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSW</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2329306 - Disclosure - Commitment and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CommitmentandContingenciesTables</Role>
      <ShortName>Commitment and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2333307 - Disclosure - Stockholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockholdersEquityTables</Role>
      <ShortName>Stockholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2338308 - Disclosure - Stock Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockBasedCompensationTables</Role>
      <ShortName>Stock Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://transphormusa.com/role/StockBasedCompensation</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - Business and Basis of Presentation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/BusinessandBasisofPresentationDetails</Role>
      <ShortName>Business and Basis of Presentation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/BusinessandBasisofPresentationPolicies</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Nexperia Arrangement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/NexperiaArrangementDetails</Role>
      <ShortName>Nexperia Arrangement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/NexperiaArrangement</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Fair Value Measurements - Fair Value Hierarchy (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/FairValueMeasurementsFairValueHierarchyDetails</Role>
      <ShortName>Fair Value Measurements - Fair Value Hierarchy (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - Fair Value Measurements - Changes in Level 3 inputs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/FairValueMeasurementsChangesinLevel3inputsDetails</Role>
      <ShortName>Fair Value Measurements - Changes in Level 3 inputs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - Fair Value Measures - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/FairValueMeasuresNarrativeDetails</Role>
      <ShortName>Fair Value Measures - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2411406 - Disclosure - Fair Value Measurements - Fair value measurement inputs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/FairValueMeasurementsFairvaluemeasurementinputsDetails</Role>
      <ShortName>Fair Value Measurements - Fair value measurement inputs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2414407 - Disclosure - Concentration of Credit Risk and Significant Customers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/ConcentrationofCreditRiskandSignificantCustomersDetails</Role>
      <ShortName>Concentration of Credit Risk and Significant Customers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/ConcentrationofCreditRiskandSignificantCustomersTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2417408 - Disclosure - Inventory (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/InventoryDetails</Role>
      <ShortName>Inventory (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/InventoryTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2420409 - Disclosure - Debts - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/DebtsAdditionalInformationDetails</Role>
      <ShortName>Debts - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2421410 - Disclosure - Debts - Notes Payable (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://transphormusa.com/role/DebtsNotesPayableDetails</Role>
      <ShortName>Debts - Notes Payable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2422411 - Disclosure - Debts - Maturities Schedule (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/DebtsMaturitiesScheduleDetails</Role>
      <ShortName>Debts - Maturities Schedule (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2425412 - Disclosure - Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSWNarrativeDetails</Role>
      <ShortName>Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSWTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2426413 - Disclosure - Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") - Income Statement Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSWIncomeStatementInformationDetails</Role>
      <ShortName>Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") - Income Statement Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSWTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2427414 - Disclosure - Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") - Summarized Financial Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSWSummarizedFinancialInformationDetails</Role>
      <ShortName>Investment in Aizu Fujitsu Semiconductor Wafer Solution Limited ("AFSW") - Summarized Financial Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/InvestmentinAizuFujitsuSemiconductorWaferSolutionLimitedAFSWTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2430415 - Disclosure - Commitment and Contingencies - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CommitmentandContingenciesNarrativeDetails</Role>
      <ShortName>Commitment and Contingencies - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2431416 - Disclosure - Commitment and Contingencies - Operating Lease Maturity Schedule (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/CommitmentandContingenciesOperatingLeaseMaturityScheduleDetails</Role>
      <ShortName>Commitment and Contingencies - Operating Lease Maturity Schedule (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2434417 - Disclosure - Stockholders' Deficit - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockholdersDeficitNarrativeDetails</Role>
      <ShortName>Stockholders' Deficit - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2435418 - Disclosure - Stockholders' Deficit - Reserved Common Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockholdersDeficitReservedCommonStockDetails</Role>
      <ShortName>Stockholders' Deficit - Reserved Common Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2436419 - Disclosure - Stockholders' Deficit - Warrants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockholdersDeficitWarrantsDetails</Role>
      <ShortName>Stockholders' Deficit - Warrants (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2439420 - Disclosure - Stock Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockBasedCompensationDetails</Role>
      <ShortName>Stock Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/StockBasedCompensationTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2440421 - Disclosure - Stock Based Compensation - Schedule of Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockBasedCompensationScheduleofOptionActivityDetails</Role>
      <ShortName>Stock Based Compensation - Schedule of Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2441422 - Disclosure - Stock Based Compensation - Restricted Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockBasedCompensationRestrictedStockDetails</Role>
      <ShortName>Stock Based Compensation - Restricted Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2442423 - Disclosure - Stock Based Compensation - Share-based Payment Agreement, Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockBasedCompensationSharebasedPaymentAgreementExpenseDetails</Role>
      <ShortName>Stock Based Compensation - Share-based Payment Agreement, Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2443424 - Disclosure - Stock Based Compensation - Unrecognized Stock-Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/StockBasedCompensationUnrecognizedStockBasedCompensationDetails</Role>
      <ShortName>Stock Based Compensation - Unrecognized Stock-Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2445425 - Disclosure - Related Party Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/RelatedPartyTransactionsDetails</Role>
      <ShortName>Related Party Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/RelatedPartyTransactions</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="tgan-20210630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2447426 - Disclosure - Subsequent Events (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://transphormusa.com/role/SubsequentEventsDetails</Role>
      <ShortName>Subsequent Events (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://transphormusa.com/role/SubsequentEvents</ParentRole>
      <Position>54</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="tgan-20210630.htm">tgan-20210630.htm</File>
    <File>exhibit101amendmentno7tolo.htm</File>
    <File>exhibit31106302021ceocerti.htm</File>
    <File>exhibit31206302021cfocerti.htm</File>
    <File>exhibit32106302021ceocfoce.htm</File>
    <File>tgan-20210630.xsd</File>
    <File>tgan-20210630_cal.xml</File>
    <File>tgan-20210630_def.xml</File>
    <File>tgan-20210630_lab.xml</File>
    <File>tgan-20210630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>tgan-20210630_g1.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.sec.gov/country/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2020-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
