<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.20.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>107</ContextCount>
  <ElementCount>312</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>36</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Condensed Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1002501 - Statement - Condensed Consolidated Statements of Comprehensive Income (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CondensedConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1003501 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CondensedConsolidatedStatementsOfStockholdersEquityParenthetical</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1004000 - Statement - Condensed Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/CondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Basis of Presentation and Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/BasisOfPresentationAndSignificantAccountingPolicies</Role>
      <ShortName>Basis of Presentation and Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2102100 - 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>10</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2103100 - 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>11</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Revenues</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/Revenues</Role>
      <ShortName>Revenues</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Accounts Receivable and Allowance for Doubtful Accounts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/AccountsReceivableAndAllowanceForDoubtfulAccounts</Role>
      <ShortName>Accounts Receivable and Allowance for Doubtful Accounts</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Goodwill and Other Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillAndOtherIntangibleAssets</Role>
      <ShortName>Goodwill and Other Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/FinancialInstruments</Role>
      <ShortName>Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2113100 - 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>18</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2114100 - 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>19</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/SegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2202201 - Disclosure - New Accounting Standards (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/NewAccountingStandardsPolicies</Role>
      <ShortName>New Accounting Standards (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/BasisOfPresentationAndSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2303301 - 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>23</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Goodwill and Other Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillAndOtherIntangibleAssetsTables</Role>
      <ShortName>Goodwill and Other Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/GoodwillAndOtherIntangibleAssets</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/FinancialInstrumentsTables</Role>
      <ShortName>Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/FinancialInstruments</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/Debt</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2312301 - 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>27</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2314301 - 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>28</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2315301 - 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>29</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2316301 - 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>30</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2403402 - 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>31</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2404401 - 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>32</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2406401 - Disclosure - Accounts Receivable and Allowance for Doubtful Accounts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/AccountsReceivableAndAllowanceForDoubtfulAccountsDetails</Role>
      <ShortName>Accounts Receivable and Allowance for Doubtful Accounts (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fticonsulting.com/role/AccountsReceivableAndAllowanceForDoubtfulAccounts</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillAndOtherIntangibleAssetsChangesInCarryingAmountOfGoodwillDetails</Role>
      <ShortName>Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Goodwill and Other Intangible Assets - Other Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillAndOtherIntangibleAssetsOtherIntangibleAssetsDetails</Role>
      <ShortName>Goodwill and Other Intangible Assets - Other Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - Goodwill and Other Intangible Assets - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillAndOtherIntangibleAssetsAdditionalInformationDetails</Role>
      <ShortName>Goodwill and Other Intangible Assets - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2409405 - Disclosure - Goodwill and Other Intangible Assets - Future Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/GoodwillAndOtherIntangibleAssetsFutureAmortizationExpenseDetails</Role>
      <ShortName>Goodwill and Other Intangible Assets - Future Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Financial Instruments - Carrying And Estimated Fair Value Of Other Financial Instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/FinancialInstrumentsCarryingAndEstimatedFairValueOfOtherFinancialInstrumentsDetail</Role>
      <ShortName>Financial Instruments - Carrying And Estimated Fair Value Of Other Financial Instruments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Financial Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/FinancialInstrumentsAdditionalInformationDetail</Role>
      <ShortName>Financial Instruments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2410404 - Disclosure - Financial Instruments - Fair Value Rollforward (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/FinancialInstrumentsFairValueRollforwardDetails</Role>
      <ShortName>Financial Instruments - Fair Value Rollforward (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Debt - Summary of Components of Debt Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DebtSummaryOfComponentsOfDebtObligationsDetails</Role>
      <ShortName>Debt - Summary of Components of Debt Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Debt - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DebtAdditionalInformationDetails</Role>
      <ShortName>Debt - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - Debt - Summary of Interest Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/DebtSummaryOfInterestExpenseDetails</Role>
      <ShortName>Debt - Summary of Interest Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2412402 - 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>44</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2412403 - 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>45</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2412404 - 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>46</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2412405 - 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>47</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2412406 - 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>48</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2414402 - 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>49</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Share-Based Compensation - Schedule Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/ShareBasedCompensationScheduleCompensationExpenseDetails</Role>
      <ShortName>Share-Based Compensation - Schedule Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2415402 - 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>51</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2415403 - Disclosure - Stockholders' Equity - Schedule of Stock Repurchases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fticonsulting.com/role/StockholdersEquityScheduleOfStockRepurchasesDetails</Role>
      <ShortName>Stockholders' Equity - Schedule of Stock Repurchases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2416402 - 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>53</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2416403 - 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>54</Position>
    </Report>
    <Report instance="fti33120-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2416404 - 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>55</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="fti33120-10q.htm">fti33120-10q.htm</File>
    <File>fcn-20200331.xsd</File>
    <File>fcn-20200331_cal.xml</File>
    <File>fcn-20200331_def.xml</File>
    <File>fcn-20200331_lab.xml</File>
    <File>fcn-20200331_pre.xml</File>
    <File>fti33120-10qex311.htm</File>
    <File>fti33120-10qex312.htm</File>
    <File>fti33120-10qex321.htm</File>
    <File>fti33120-10qex322.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/us-gaap/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
