<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.4</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>372</ContextCount>
  <ElementCount>511</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>117</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_StatementConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100030 - Statement - Consolidated Statements of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/StatementConsolidatedStatementsOfIncome</Role>
      <ShortName>Consolidated Statements of Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100040 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100050 - Statement - Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_StatementConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100060 - Statement - Consolidated Statements of Stockholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_StatementConsolidatedStatementsOfStockholdersEquityParenthetical</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100070 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Overview and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureOverviewAndBasisOfPresentation</Role>
      <ShortName>Overview and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Equity and Debt Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityAndDebtSecurities</Role>
      <ShortName>Equity and Debt Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100110 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Fixed Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFixedAssets</Role>
      <ShortName>Fixed Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Other Significant Balance Sheet Accounts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureOtherSignificantBalanceSheetAccounts</Role>
      <ShortName>Other Significant Balance Sheet Accounts</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Reporting Segment and Geographic Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureReportingSegmentAndGeographicInformation</Role>
      <ShortName>Reporting Segment and Geographic Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Debt, Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureDebtCommitmentsAndContingencies</Role>
      <ShortName>Debt, Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100170 - Disclosure - Equity-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensation</Role>
      <ShortName>Equity-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100180 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100190 - Disclosure - Income per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureIncomePerShare</Role>
      <ShortName>Income per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Retirement Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureRetirementPlans</Role>
      <ShortName>Retirement Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Related Party</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureRelatedParty</Role>
      <ShortName>Related Party</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Business Combinations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureBusinessCombinations</Role>
      <ShortName>Business Combinations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100240 - Disclosure - Stock Repurchase Program</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureStockRepurchaseProgram1</Role>
      <ShortName>Stock Repurchase Program</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Goodwill and Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureGoodwillAndIntangibleAssets1</Role>
      <ShortName>Goodwill and Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100260 - Disclosure - Selected Quarterly Financial Data (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSelectedQuarterlyFinancialDataUnaudited</Role>
      <ShortName>Selected Quarterly Financial Data (Unaudited)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100270 - Disclosure - Subsequent Event</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSubsequentEvent</Role>
      <ShortName>Subsequent Event</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100300 - Disclosure - Equity and Debt Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityAndDebtSecuritiesTables</Role>
      <ShortName>Equity and Debt Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityAndDebtSecurities</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFairValueMeasurements</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Fixed Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFixedAssetsTables</Role>
      <ShortName>Fixed Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFixedAssets</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100330 - Disclosure - Other Significant Balance Sheet Accounts (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureOtherSignificantBalanceSheetAccountsTables</Role>
      <ShortName>Other Significant Balance Sheet Accounts (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureOtherSignificantBalanceSheetAccounts</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100340 - Disclosure - Reporting Segment and Geographic Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureReportingSegmentAndGeographicInformationTables</Role>
      <ShortName>Reporting Segment and Geographic Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureReportingSegmentAndGeographicInformation</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100350 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeases</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Equity-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensationTables</Role>
      <ShortName>Equity-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensation</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>100370 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxes</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>100380 - Disclosure - Income Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureIncomePerShareTables</Role>
      <ShortName>Income Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>100390 - Disclosure - Business Combinations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureBusinessCombinationsTables</Role>
      <ShortName>Business Combinations (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureBusinessCombinations</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>100400 - Disclosure - Goodwill and Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsTables</Role>
      <ShortName>Goodwill and Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureGoodwillAndIntangibleAssets1</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>100410 - Disclosure - Selected Quarterly Financial Data (Unaudited) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSelectedQuarterlyFinancialDataUnauditedTables</Role>
      <ShortName>Selected Quarterly Financial Data (Unaudited) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSelectedQuarterlyFinancialDataUnaudited</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>100420 - Disclosure - Summary of Significant Accounting Policies - Roll-Forward of Activity in Allowance for Credit Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesRollForwardOfActivityInAllowanceForCreditLossesDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Roll-Forward of Activity in Allowance for Credit Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>100430 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>100440 - Disclosure - Summary of Significant Accounting Policies - Summary of Revenue from Contracts with Customers by Payor Type (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesSummaryOfRevenueFromContractsWithCustomersByPayorTypeDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Summary of Revenue from Contracts with Customers by Payor Type (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>100450 - Disclosure - Equity and Debt Securities - Summary of Equity and Debt Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityAndDebtSecuritiesSummaryOfEquityAndDebtSecuritiesDetails</Role>
      <ShortName>Equity and Debt Securities - Summary of Equity and Debt Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>100460 - Disclosure - Equity and Debt Securities - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityAndDebtSecuritiesAdditionalInformationDetails</Role>
      <ShortName>Equity and Debt Securities - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>100470 - Disclosure - Fair Value Measurements - Information about Financial Assets Measured at Fair Value on Recurring Basis Based on Three-Tier Fair Value Hierarchy (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFairValueMeasurementsInformationAboutFinancialAssetsMeasuredAtFairValueOnRecurringBasisBasedOnThreeTierFairValueHierarchyDetails</Role>
      <ShortName>Fair Value Measurements - Information about Financial Assets Measured at Fair Value on Recurring Basis Based on Three-Tier Fair Value Hierarchy (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>100480 - Disclosure - Fair Value Measurements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFairValueMeasurementsAdditionalInformationDetails</Role>
      <ShortName>Fair Value Measurements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>100490 - Disclosure - Fixed Assets - Major Classes of Fixed Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFixedAssetsMajorClassesOfFixedAssetsDetails</Role>
      <ShortName>Fixed Assets - Major Classes of Fixed Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>100500 - Disclosure - Fixed Assets - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureFixedAssetsAdditionalInformationDetails</Role>
      <ShortName>Fixed Assets - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>100510 - Disclosure - Other Significant Balance Sheet Accounts - Schedule of Other Current Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureOtherSignificantBalanceSheetAccountsScheduleOfOtherCurrentAssetsDetails</Role>
      <ShortName>Other Significant Balance Sheet Accounts - Schedule of Other Current Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>100520 - Disclosure - Other Significant Balance Sheet Accounts - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureOtherSignificantBalanceSheetAccountsAdditionalInformationDetails</Role>
      <ShortName>Other Significant Balance Sheet Accounts - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>100530 - Disclosure - Reporting Segment and Geographical Information - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureReportingSegmentAndGeographicalInformationAdditionalInformationDetails</Role>
      <ShortName>Reporting Segment and Geographical Information - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>100540 - Disclosure - Reporting Segment and Geographical Information - Summary of Revenue by Geographic Region (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureReportingSegmentAndGeographicalInformationSummaryOfRevenueByGeographicRegionDetails</Role>
      <ShortName>Reporting Segment and Geographical Information - Summary of Revenue by Geographic Region (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>100550 - Disclosure - Debt, Commitments and Contingencies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureDebtCommitmentsAndContingenciesAdditionalInformationDetails</Role>
      <ShortName>Debt, Commitments and Contingencies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>100560 - Disclosure - Leases - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeasesAdditionalInformationDetails</Role>
      <ShortName>Leases - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>100570 - Disclosure - Leases - Schedule of Operating and Finance Lease Right-of-Use Asset, Short-term Lease Liabilities, and Long-term Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeasesScheduleOfOperatingAndFinanceLeaseRightOfUseAssetShortTermLeaseLiabilitiesAndLongTermLeaseLiabilitiesDetails</Role>
      <ShortName>Leases - Schedule of Operating and Finance Lease Right-of-Use Asset, Short-term Lease Liabilities, and Long-term Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>100580 - Disclosure - Leases - Schedule of Operating and Financing Lease Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureLeasesScheduleOfOperatingAndFinancingLeaseExpenseDetails</Role>
      <ShortName>Leases - Schedule of Operating and Financing Lease Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>100590 - Disclosure - Leases - Schedule of Supplemental Information Related to Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeasesScheduleOfSupplementalInformationRelatedToLeasesDetails</Role>
      <ShortName>Leases - Schedule of Supplemental Information Related to Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>100600 - Disclosure - Leases - Schedule of Maturity Analysis of Operating and Finance Lease Liabilities using Undiscounted Cash Flows on an Annual Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeasesScheduleOfMaturityAnalysisOfOperatingAndFinanceLeaseLiabilitiesUsingUndiscountedCashFlowsOnAnnualBasisDetails</Role>
      <ShortName>Leases - Schedule of Maturity Analysis of Operating and Finance Lease Liabilities using Undiscounted Cash Flows on an Annual Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>100620 - Disclosure - Leases - Schedule of Lease Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeasesScheduleOfLeaseIncomeDetails</Role>
      <ShortName>Leases - Schedule of Lease Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>100630 - Disclosure - Leases - Schedule of Future Fixed Lease Payments from Tenants for All Noncancelable Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureLeasesScheduleOfFutureFixedLeasePaymentsFromTenantsForAllNoncancelableOperatingLeasesDetails</Role>
      <ShortName>Leases - Schedule of Future Fixed Lease Payments from Tenants for All Noncancelable Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>100640 - Disclosure - Equity-Based Compensation - Summary of Equity-Based Compensation Expenses as Part of Cost of Revenue and Operating Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensationSummaryOfEquityBasedCompensationExpensesAsPartOfCostOfRevenueAndOperatingExpensesDetails</Role>
      <ShortName>Equity-Based Compensation - Summary of Equity-Based Compensation Expenses as Part of Cost of Revenue and Operating Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>100650 - Disclosure - Equity-Based Compensation - Summary of Activity for Options to Acquire Common Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensationSummaryOfActivityForOptionsToAcquireCommonSharesDetails</Role>
      <ShortName>Equity-Based Compensation - Summary of Activity for Options to Acquire Common Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>100660 - Disclosure - Equity-Based Compensation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensationAdditionalInformationDetails</Role>
      <ShortName>Equity-Based Compensation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>100670 - Disclosure - Equity-Based Compensation - Summary of Activity for RSUs Relating to Shares of Company's Common Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensationSummaryOfActivityForRsusRelatingToSharesOfCompanySCommonStockDetails</Role>
      <ShortName>Equity-Based Compensation - Summary of Activity for RSUs Relating to Shares of Company's Common Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>100680 - Disclosure - Equity-Based Compensation - Summary of Weighted-Average Assumptions Used to Estimate Fair Value of Options to Acquire Shares of Company's Common Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureEquityBasedCompensationSummaryOfWeightedAverageAssumptionsUsedToEstimateFairValueOfOptionsToAcquireSharesOfCompanySCommonStockDetails</Role>
      <ShortName>Equity-Based Compensation - Summary of Weighted-Average Assumptions Used to Estimate Fair Value of Options to Acquire Shares of Company's Common Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>100690 - Disclosure - Income Taxes - Summary of Income (Loss) Before Income Taxes and Equity Loss in Investee and Gain (Loss) on Equity-Method Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxesSummaryOfIncomeLossBeforeIncomeTaxesAndEquityLossInInvesteeAndGainLossOnEquityMethodInvestmentsDetails</Role>
      <ShortName>Income Taxes - Summary of Income (Loss) Before Income Taxes and Equity Loss in Investee and Gain (Loss) on Equity-Method Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>100700 - Disclosure - Income Taxes - Income Tax Expense (Benefit) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxesIncomeTaxExpenseBenefitDetails</Role>
      <ShortName>Income Taxes - Income Tax Expense (Benefit) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>100710 - Disclosure - Income Taxes - Reconciliation of Difference between Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxesReconciliationOfDifferenceBetweenFederalStatutoryIncomeTaxRateAndEffectiveIncomeTaxRateDetails</Role>
      <ShortName>Income Taxes - Reconciliation of Difference between Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>100720 - Disclosure - Income Taxes - Summary of Elements of Deferred Tax Assets (Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxesSummaryOfElementsOfDeferredTaxAssetsLiabilitiesDetails</Role>
      <ShortName>Income Taxes - Summary of Elements of Deferred Tax Assets (Liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>100730 - Disclosure - Income Taxes - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxesAdditionalInformationDetails</Role>
      <ShortName>Income Taxes - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>100740 - Disclosure - Income Taxes - Reconciliation of Gross Unrecognized Tax Benefits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureIncomeTaxesReconciliationOfGrossUnrecognizedTaxBenefitsDetails</Role>
      <ShortName>Income Taxes - Reconciliation of Gross Unrecognized Tax Benefits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>100750 - Disclosure - Income per Share - Reconciliation of Basic and Diluted Income Per Share Computations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureIncomePerShareReconciliationOfBasicAndDilutedIncomePerShareComputationsDetails</Role>
      <ShortName>Income per Share - Reconciliation of Basic and Diluted Income Per Share Computations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>100760 - Disclosure - Income per Share - Anti-dilutive Securities Excluded from Calculation of Diluted Income Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureIncomePerShareAntidilutiveSecuritiesExcludedFromCalculationOfDilutedIncomePerShareDetails</Role>
      <ShortName>Income per Share - Anti-dilutive Securities Excluded from Calculation of Diluted Income Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>100770 - Disclosure - Retirement Plans - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureRetirementPlansAdditionalInformationDetails</Role>
      <ShortName>Retirement Plans - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>100780 - Disclosure - Related Party - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureRelatedPartyAdditionalInformationDetails</Role>
      <ShortName>Related Party - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>100790 - Disclosure - Business Combinations - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureBusinessCombinationsAdditionalInformationDetails</Role>
      <ShortName>Business Combinations - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>100800 - Disclosure - Business Combinations - Summary of Consideration Paid and Amount of Assets Acquired and Liabilities Assumed (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureBusinessCombinationsSummaryOfConsiderationPaidAndAmountOfAssetsAcquiredAndLiabilitiesAssumedDetails</Role>
      <ShortName>Business Combinations - Summary of Consideration Paid and Amount of Assets Acquired and Liabilities Assumed (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>100810 - Disclosure - Business Combinations - Summary of Unaudited Pro Forma Financial Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureBusinessCombinationsSummaryOfUnauditedProFormaFinancialInformationDetails</Role>
      <ShortName>Business Combinations - Summary of Unaudited Pro Forma Financial Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>100820 - Disclosure - Stock Repurchase Program - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureStockRepurchaseProgramAdditionalInformationDetails</Role>
      <ShortName>Stock Repurchase Program - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>100840 - Disclosure - Goodwill and Intangible Assets - Summaries of Goodwill and Acquisitions-Related Intangibles Balances (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsSummariesOfGoodwillAndAcquisitionsrelatedIntangiblesBalancesDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Summaries of Goodwill and Acquisitions-Related Intangibles Balances (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>100860 - Disclosure - Goodwill and Intangible Assets - Summary of Carrying Amount of Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfCarryingAmountOfGoodwillDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Summary of Carrying Amount of Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>100870 - Disclosure - Goodwill and Intangible Assets - Summary of Annual Amortization Expense For Acquisition-Related Intangibles (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfAnnualAmortizationExpenseForAcquisitionrelatedIntangiblesDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Summary of Annual Amortization Expense For Acquisition-Related Intangibles (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="flgt-20221231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>100880 - Disclosure - Selected Quarterly Financial Data (Unaudited) - Unaudited Quarterly Data (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSelectedQuarterlyFinancialDataUnauditedUnauditedQuarterlyDataDetails</Role>
      <ShortName>Selected Quarterly Financial Data (Unaudited) - Unaudited Quarterly Data (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://fulgentdiagnostics.com/20221231/taxonomy/role/Role_DisclosureSelectedQuarterlyFinancialDataUnauditedTables</ParentRole>
      <Position>85</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 2 fact(s) appearing in ix:hidden were eligible for transformation: us-gaap:FiniteLivedIntangibleAssetUsefulLife, us-gaap:PreferredStockRedemptionDate -  flgt-20221231.htm 8</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-K" original="flgt-20221231.htm">flgt-20221231.htm</File>
    <File>flgt-20221231.xsd</File>
    <File>flgt-20221231_cal.xml</File>
    <File>flgt-20221231_def.xml</File>
    <File>flgt-20221231_lab.xml</File>
    <File>flgt-20221231_pre.xml</File>
    <File>flgt-ex10_46.htm</File>
    <File>flgt-ex10_48.htm</File>
    <File>flgt-ex10_49.htm</File>
    <File>flgt-ex10_50.htm</File>
    <File>flgt-ex10_51.htm</File>
    <File>flgt-ex10_52.htm</File>
    <File>flgt-ex21_1.htm</File>
    <File>flgt-ex23_1.htm</File>
    <File>flgt-ex31_1.htm</File>
    <File>flgt-ex31_2.htm</File>
    <File>flgt-ex32_1.htm</File>
    <File>flgt-ex4_3.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>img231266967_0.jpg</File>
    <File>img231266967_1.jpg</File>
    <File>img231266967_10.jpg</File>
    <File>img231266967_11.jpg</File>
    <File>img231266967_2.jpg</File>
    <File>img231266967_3.jpg</File>
    <File>img231266967_4.jpg</File>
    <File>img231266967_5.jpg</File>
    <File>img231266967_6.jpg</File>
    <File>img231266967_7.jpg</File>
    <File>img231266967_8.jpg</File>
    <File>img231266967_9.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1336">http://fasb.org/us-gaap/2022</BaseTaxonomy>
    <BaseTaxonomy items="37">http://xbrl.sec.gov/dei/2022</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
