<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.4</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>208</ContextCount>
  <ElementCount>428</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>69</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0000002 - Document - Audit Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/AuditInformation</Role>
      <ShortName>Audit Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952151 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952152 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952153 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ConsolidatedStatementsofComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952154 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ConsolidatedStatementsofComprehensiveIncomeParenthetical</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952155 - Statement - Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ConsolidatedStatementsofStockholdersEquity</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952156 - Statement - Consolidated Statements of Stockholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ConsolidatedStatementsofStockholdersEquityParenthetical</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952157 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ConsolidatedStatementsofCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952158 - Disclosure - Description of Business and Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPolicies</Role>
      <ShortName>Description of Business and Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - New Accounting Standards</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/NewAccountingStandards</Role>
      <ShortName>New Accounting Standards</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Earnings per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/EarningsperCommonShare</Role>
      <ShortName>Earnings per Common Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Revenues</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/Revenues</Role>
      <ShortName>Revenues</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - Accounts Receivable and Allowance for Expected Credit Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/AccountsReceivableandAllowanceforExpectedCreditLosses</Role>
      <ShortName>Accounts Receivable and Allowance for Expected Credit Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Special Charges</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SpecialCharges</Role>
      <ShortName>Special Charges</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Share-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensation</Role>
      <ShortName>Share-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Interest Income and Other</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/InterestIncomeandOther</Role>
      <ShortName>Interest Income and Other</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Balance Sheet Details</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/BalanceSheetDetails</Role>
      <ShortName>Balance Sheet Details</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Property and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/PropertyandEquipment</Role>
      <ShortName>Property and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Goodwill and Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillandIntangibleAssets</Role>
      <ShortName>Goodwill and Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - Notes Receivable from Employees</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.fticonsulting.com/role/NotesReceivablefromEmployees</Role>
      <ShortName>Notes Receivable from Employees</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9952171 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9952172 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CommitmentsandContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9952173 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9952174 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9952175 - Disclosure - Employee Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/EmployeeBenefitPlans</Role>
      <ShortName>Employee Benefit Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9952176 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995447 - Disclosure - Insider Trading Policies and Procedures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc</Role>
      <ShortName>Insider Trading Policies and Procedures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure</Role>
      <ShortName>Cybersecurity Risk Management and Strategy Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - Description of Business and Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Description of Business and Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPolicies</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - Earnings per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/EarningsperCommonShareTables</Role>
      <ShortName>Earnings per Common Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/EarningsperCommonShare</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - Accounts Receivable and Allowance for Expected Credit Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/AccountsReceivableandAllowanceforExpectedCreditLossesTables</Role>
      <ShortName>Accounts Receivable and Allowance for Expected Credit Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/AccountsReceivableandAllowanceforExpectedCreditLosses</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - Special Charges (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SpecialChargesTables</Role>
      <ShortName>Special Charges (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/SpecialCharges</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - Share-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationTables</Role>
      <ShortName>Share-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/ShareBasedCompensation</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - Interest Income and Other (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/InterestIncomeandOtherTables</Role>
      <ShortName>Interest Income and Other (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/InterestIncomeandOther</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - Balance Sheet Details (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/BalanceSheetDetailsTables</Role>
      <ShortName>Balance Sheet Details (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/BalanceSheetDetails</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - Property and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/PropertyandEquipmentTables</Role>
      <ShortName>Property and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/PropertyandEquipment</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - Goodwill and Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillandIntangibleAssetsTables</Role>
      <ShortName>Goodwill and Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/GoodwillandIntangibleAssets</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - Notes Receivable from Employees (Tables)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.fticonsulting.com/role/NotesReceivablefromEmployeesTables</Role>
      <ShortName>Notes Receivable from Employees (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/NotesReceivablefromEmployees</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/Leases</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/IncomeTaxes</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - Stockholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/StockholdersEquityTables</Role>
      <ShortName>Stockholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/StockholdersEquity</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - Segment Reporting (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReportingTables</Role>
      <ShortName>Segment Reporting (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/SegmentReporting</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - Description of Business and Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails</Role>
      <ShortName>Description of Business and Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - Earnings per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/EarningsperCommonShareDetails</Role>
      <ShortName>Earnings per Common Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/EarningsperCommonShareTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - Revenues (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/RevenuesDetails</Role>
      <ShortName>Revenues (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/Revenues</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - Accounts Receivable and Allowance for Expected Credit Losses - Accounts Receivable, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/AccountsReceivableandAllowanceforExpectedCreditLossesAccountsReceivableNetDetails</Role>
      <ShortName>Accounts Receivable and Allowance for Expected Credit Losses - Accounts Receivable, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - Accounts Receivable and Allowance for Expected Credit Losses - Accounts Receivable, Writeoff (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/AccountsReceivableandAllowanceforExpectedCreditLossesAccountsReceivableWriteoffDetails</Role>
      <ShortName>Accounts Receivable and Allowance for Expected Credit Losses - Accounts Receivable, Writeoff (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - Special Charges - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SpecialChargesAdditionalInformationDetails</Role>
      <ShortName>Special Charges - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - Special Charges - Schedule of Special Charges by Segment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SpecialChargesScheduleofSpecialChargesbySegmentDetails</Role>
      <ShortName>Special Charges - Schedule of Special Charges by Segment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - Share-Based Compensation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationAdditionalInformationDetails</Role>
      <ShortName>Share-Based Compensation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - Share-Based Compensation - Share-based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationSharebasedCompensationExpenseDetails</Role>
      <ShortName>Share-Based Compensation - Share-based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - Share-Based Compensation - Unvested Restricted Share Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationUnvestedRestrictedShareActivityDetails</Role>
      <ShortName>Share-Based Compensation - Unvested Restricted Share Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - Share-Based Compensation - Restricted Stock Unit Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationRestrictedStockUnitActivityDetails</Role>
      <ShortName>Share-Based Compensation - Restricted Stock Unit Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - Share-Based Compensation - Performance Stock Units Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationPerformanceStockUnitsActivityDetails</Role>
      <ShortName>Share-Based Compensation - Performance Stock Units Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - Share-Based Compensation - Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationStockOptionActivityDetails</Role>
      <ShortName>Share-Based Compensation - Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - Interest Income and Other (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/InterestIncomeandOtherDetails</Role>
      <ShortName>Interest Income and Other (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/InterestIncomeandOtherTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - Balance Sheet Details (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/BalanceSheetDetailsDetails</Role>
      <ShortName>Balance Sheet Details (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/BalanceSheetDetailsTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - Property and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/PropertyandEquipmentDetails</Role>
      <ShortName>Property and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/PropertyandEquipmentTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - Goodwill and Intangible Assets - Changes in Carrying Amounts of Goodwill by Operating Segment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillandIntangibleAssetsChangesinCarryingAmountsofGoodwillbyOperatingSegmentDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Changes in Carrying Amounts of Goodwill by Operating Segment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - Goodwill and Intangible Assets - Intangible assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillandIntangibleAssetsIntangibleassetsDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Intangible assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - Goodwill and Intangible Assets - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillandIntangibleAssetsAdditionalInformationDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - Goodwill and Intangible Assets - Future Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillandIntangibleAssetsFutureAmortizationExpenseDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Future Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - Notes Receivable from Employees - Changes in Carrying Amount of Notes Receivable From Employees (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.fticonsulting.com/role/NotesReceivablefromEmployeesChangesinCarryingAmountofNotesReceivableFromEmployeesDetails</Role>
      <ShortName>Notes Receivable from Employees - Changes in Carrying Amount of Notes Receivable From Employees (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - Notes Receivable from Employees - Additional information (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.fticonsulting.com/role/NotesReceivablefromEmployeesAdditionalinformationDetails</Role>
      <ShortName>Notes Receivable from Employees - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DebtDetails</Role>
      <ShortName>Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/Debt</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - Leases - Lease Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/LeasesLeaseAssetsandLiabilitiesDetails</Role>
      <ShortName>Leases - Lease Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - Leases - Lease Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/LeasesLeaseCostDetails</Role>
      <ShortName>Leases - Lease Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - Leases - Maturity Analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/LeasesMaturityAnalysisDetails</Role>
      <ShortName>Leases - Maturity Analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - Leases - Cash Paid For Operating Leases and Noncash Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/LeasesCashPaidForOperatingLeasesandNoncashInformationDetails</Role>
      <ShortName>Leases - Cash Paid For Operating Leases and Noncash Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - Leases - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/LeasesAdditionalInformationDetails</Role>
      <ShortName>Leases - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CommitmentsandContingenciesAdditionalInformationDetail</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesComponentsofDeferredTaxAssetsandLiabilitiesDetails</Role>
      <ShortName>Income Taxes - Components of Deferred Tax Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - Income Taxes - Deferred Tax Assets Valuation Allowance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesDeferredTaxAssetsValuationAllowanceDetails</Role>
      <ShortName>Income Taxes - Deferred Tax Assets Valuation Allowance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - Income Taxes - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesAdditionalInformationDetails</Role>
      <ShortName>Income Taxes - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - Income Taxes - Components of Income Before Income Tax Provision from Continuing Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesComponentsofIncomeBeforeIncomeTaxProvisionfromContinuingOperationsDetails</Role>
      <ShortName>Income Taxes - Components of Income Before Income Tax Provision from Continuing Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - Income Taxes - Components of Income Tax Provision from Continuing Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesComponentsofIncomeTaxProvisionfromContinuingOperationsDetails</Role>
      <ShortName>Income Taxes - Components of Income Tax Provision from Continuing Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - Income Taxes - Components of Cash Paid For Income Taxes and Tax Credits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesComponentsofCashPaidForIncomeTaxesandTaxCreditsDetails</Role>
      <ShortName>Income Taxes - Components of Cash Paid For Income Taxes and Tax Credits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - Income Taxes - Income Tax Provision From Continuing Operations Resulted In Effective Tax Rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesIncomeTaxProvisionFromContinuingOperationsResultedInEffectiveTaxRatesDetails</Role>
      <ShortName>Income Taxes - Income Tax Provision From Continuing Operations Resulted In Effective Tax Rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - Income Taxes - Income Tax Provision from Continuing Operations Resulted in Effective Tax Rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/IncomeTaxesIncomeTaxProvisionfromContinuingOperationsResultedinEffectiveTaxRatesDetails</Role>
      <ShortName>Income Taxes - Income Tax Provision from Continuing Operations Resulted in Effective Tax Rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - Stockholders' Equity - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/StockholdersEquityAdditionalInformationDetails</Role>
      <ShortName>Stockholders' Equity - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - Stockholders' Equity - Stock Repurchases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/StockholdersEquityStockRepurchasesDetails</Role>
      <ShortName>Stockholders' Equity - Stock Repurchases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9955564 - Disclosure - Employee Benefit Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/EmployeeBenefitPlansDetails</Role>
      <ShortName>Employee Benefit Plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/EmployeeBenefitPlans</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9955565 - Disclosure - Segment Reporting - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReportingAdditionalInformationDetails</Role>
      <ShortName>Segment Reporting - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9955566 - Disclosure - Segment Reporting - Revenues and Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization for Reportable Segments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReportingRevenuesandAdjustedSegmentEarningsbeforeInterestTaxesDepreciationandAmortizationforReportableSegmentsDetails</Role>
      <ShortName>Segment Reporting - Revenues and Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization for Reportable Segments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9955567 - Disclosure - Segment Reporting - Reconciliation of Net Income To Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReportingReconciliationofNetIncomeToAdjustedSegmentEarningsbeforeInterestTaxesDepreciationandAmortizationDetails</Role>
      <ShortName>Segment Reporting - Reconciliation of Net Income To Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>9955568 - Disclosure - Segment Reporting - Revenues Based on Location of Legal Entity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReportingRevenuesBasedonLocationofLegalEntityDetails</Role>
      <ShortName>Segment Reporting - Revenues Based on Location of Legal Entity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="fcn-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>9955569 - Disclosure - Segment Reporting - Information on Long-Lived Assets and Net Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReportingInformationonLongLivedAssetsandNetAssetsDetails</Role>
      <ShortName>Segment Reporting - Information on Long-Lived Assets and Net Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</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-K" isDefinitelyFs="true" isUsgaap="true" original="fcn-20251231.htm">fcn-20251231.htm</File>
    <File>fcn-20251231.xsd</File>
    <File>fcn-20251231_cal.xml</File>
    <File>fcn-20251231_def.xml</File>
    <File>fcn-20251231_lab.xml</File>
    <File>fcn-20251231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="996">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="16">http://xbrl.sec.gov/cyd/2025</BaseTaxonomy>
    <BaseTaxonomy items="38">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="5">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
