<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>82</ContextCount>
  <ElementCount>219</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>32</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>995200090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>995200100 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/StatementCondensedConsolidatedBalanceSheets</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>995200105 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/StatementCondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>995200200 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/StatementCondensedConsolidatedStatementsOfOperations</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>995200300 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/StatementCondensedConsolidatedStatementsOfShareholdersEquity</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>995200400 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/StatementCondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>995210101 - Disclosure - Basis of Presentation of Financial Statements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureBasisOfPresentationOfFinancialStatements</Role>
      <ShortName>Basis of Presentation of Financial Statements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>995210201 - Disclosure - New Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureNewAccountingPronouncements</Role>
      <ShortName>New Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995210301 - Disclosure - Revenue</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureRevenue</Role>
      <ShortName>Revenue</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995210401 - Disclosure - Gold and Silver Rounds/Bullion</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureGoldAndSilverRoundsBullion</Role>
      <ShortName>Gold and Silver Rounds/Bullion</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995210501 - Disclosure - Inventories</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureInventories</Role>
      <ShortName>Inventories</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995210601 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995210701 - Disclosure - Prepaid Expenses and Other Current Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssets</Role>
      <ShortName>Prepaid Expenses and Other Current Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995210801 - Disclosure - Property, Plant and Mine Development, net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosurePropertyPlantAndMineDevelopmentNet</Role>
      <ShortName>Property, Plant and Mine Development, net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995210901 - Disclosure - Other Current Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureOtherCurrentLiabilities</Role>
      <ShortName>Other Current Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995211001 - Disclosure - Asset Retirement Obligation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureAssetRetirementObligation</Role>
      <ShortName>Asset Retirement Obligation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995211101 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureLeases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995211201 - Disclosure - Other Expense (Income), Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureOtherExpenseIncomeNet</Role>
      <ShortName>Other Expense (Income), Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995211301 - Disclosure - Net (Loss) Income per Common Share Attributable to Fortitude Shareholders</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureNetLossIncomePerCommonShareAttributableToFortitudeShareholders</Role>
      <ShortName>Net (Loss) Income per Common Share Attributable to Fortitude Shareholders</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995211401 - Disclosure - Fair Value Measurement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureFairValueMeasurement</Role>
      <ShortName>Fair Value Measurement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995211501 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureStockBasedCompensation</Role>
      <ShortName>Stock-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995211601 - Disclosure - Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureShareholdersEquity</Role>
      <ShortName>Shareholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.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>24</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>99920102 - Disclosure - Basis of Presentation of Financial Statements (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureBasisOfPresentationOfFinancialStatementsPolicies</Role>
      <ShortName>Basis of Presentation of Financial Statements (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureNewAccountingPronouncements</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>99930303 - Disclosure - Revenue (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureRevenueTables</Role>
      <ShortName>Revenue (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureRevenue</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>99930403 - Disclosure - Gold and Silver Rounds/Bullion (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureGoldAndSilverRoundsBullionTables</Role>
      <ShortName>Gold and Silver Rounds/Bullion (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureGoldAndSilverRoundsBullion</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>99930503 - Disclosure - Inventories (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureInventoriesTables</Role>
      <ShortName>Inventories (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureInventories</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>99930703 - Disclosure - Prepaid Expenses and Other Current Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssetsTables</Role>
      <ShortName>Prepaid Expenses and Other Current Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssets</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>99930803 - Disclosure - Property, Plant and Mine Development, net (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosurePropertyPlantAndMineDevelopmentNetTables</Role>
      <ShortName>Property, Plant and Mine Development, net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosurePropertyPlantAndMineDevelopmentNet</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>99930903 - Disclosure - Other Current Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureOtherCurrentLiabilitiesTables</Role>
      <ShortName>Other Current Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureOtherCurrentLiabilities</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>99931003 - Disclosure - Asset Retirement Obligation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureAssetRetirementObligationTables</Role>
      <ShortName>Asset Retirement Obligation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureAssetRetirementObligation</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>99931103 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureLeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureLeases</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>99931203 - Disclosure - Other Expense (Income), Net (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureOtherExpenseIncomeNetTables</Role>
      <ShortName>Other Expense (Income), Net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureOtherExpenseIncomeNet</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>99931303 - Disclosure - Net (Loss) Income per Common Share Attributable to Fortitude Shareholders (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureNetLossIncomePerCommonShareAttributableToFortitudeShareholdersTables</Role>
      <ShortName>Net (Loss) Income per Common Share Attributable to Fortitude Shareholders (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureNetLossIncomePerCommonShareAttributableToFortitudeShareholders</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>99931403 - Disclosure - Fair Value Measurement (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureFairValueMeasurementTables</Role>
      <ShortName>Fair Value Measurement (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureFairValueMeasurement</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>99931503 - Disclosure - Stock-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureStockBasedCompensationTables</Role>
      <ShortName>Stock-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureStockBasedCompensation</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>99940101 - Disclosure - Basis of Presentation of Financial Statements - Operating Segments and Related Disclosures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureBasisOfPresentationOfFinancialStatementsOperatingSegmentsAndRelatedDisclosuresDetails</Role>
      <ShortName>Basis of Presentation of Financial Statements - Operating Segments and Related Disclosures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>99940102 - Disclosure - Basis of Presentation of Financial Statements - Noncontrolling Interests (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureBasisOfPresentationOfFinancialStatementsNoncontrollingInterestsDetails</Role>
      <ShortName>Basis of Presentation of Financial Statements - Noncontrolling Interests (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>99940301 - Disclosure - Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureRevenueDetails</Role>
      <ShortName>Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureRevenueTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>99940401 - Disclosure - Gold and Silver Rounds/Bullion (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureGoldAndSilverRoundsBullionDetails</Role>
      <ShortName>Gold and Silver Rounds/Bullion (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureGoldAndSilverRoundsBullionTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>99940501 - Disclosure - Inventories - Current (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureInventoriesCurrentDetails</Role>
      <ShortName>Inventories - Current (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>99940502 - Disclosure - Inventories - Non-current (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureInventoriesNonCurrentDetails</Role>
      <ShortName>Inventories - Non-current (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>99940601 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureIncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>99940701 - Disclosure - Prepaid Expenses and Other Current Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssetsDetails</Role>
      <ShortName>Prepaid Expenses and Other Current Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssetsTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>99940801 - Disclosure - Property, Plant and Mine Development, net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosurePropertyPlantAndMineDevelopmentNetDetails</Role>
      <ShortName>Property, Plant and Mine Development, net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosurePropertyPlantAndMineDevelopmentNetTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>99940901 - Disclosure - Other Current Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureOtherCurrentLiabilitiesDetails</Role>
      <ShortName>Other Current Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureOtherCurrentLiabilitiesTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>99941001 - Disclosure - Asset Retirement Obligation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureAssetRetirementObligationDetails</Role>
      <ShortName>Asset Retirement Obligation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureAssetRetirementObligationTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>99941002 - Disclosure - Asset Retirement Obligation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureAssetRetirementObligationAdditionalInformationDetails</Role>
      <ShortName>Asset Retirement Obligation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>99941101 - Disclosure - Leases - Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureLeasesOperatingLeasesDetails</Role>
      <ShortName>Leases - Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>99941102 - Disclosure - Leases - Finance Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureLeasesFinanceLeasesDetails</Role>
      <ShortName>Leases - Finance Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>99941103 - Disclosure - Leases - Finance Leases - Minimum Annual Payments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureLeasesFinanceLeasesMinimumAnnualPaymentsDetails</Role>
      <ShortName>Leases - Finance Leases - Minimum Annual Payments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>99941104 - Disclosure - Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureLeasesDetails</Role>
      <ShortName>Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureLeasesTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>99941201 - Disclosure - Other Expense (Income), Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureOtherExpenseIncomeNetDetails</Role>
      <ShortName>Other Expense (Income), Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureOtherExpenseIncomeNetTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>99941301 - Disclosure - Net (Loss) Income per Common Share Attributable to Fortitude Shareholders - Antidilutive Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureNetLossIncomePerCommonShareAttributableToFortitudeShareholdersAntidilutiveSharesDetails</Role>
      <ShortName>Net (Loss) Income per Common Share Attributable to Fortitude Shareholders - Antidilutive Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureNetLossIncomePerCommonShareAttributableToFortitudeShareholdersTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>99941302 - Disclosure - Net (Loss) Income per Common Share Attributable to Fortitude Shareholders (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureNetLossIncomePerCommonShareAttributableToFortitudeShareholdersDetails</Role>
      <ShortName>Net (Loss) Income per Common Share Attributable to Fortitude Shareholders (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureNetLossIncomePerCommonShareAttributableToFortitudeShareholdersTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>99941401 - Disclosure - Fair Value Measurement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureFairValueMeasurementDetails</Role>
      <ShortName>Fair Value Measurement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureFairValueMeasurementTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>99941402 - Disclosure - Fair Value Measurement - Changes in the fair value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureFairValueMeasurementChangesInFairValueDetails</Role>
      <ShortName>Fair Value Measurement - Changes in the fair value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>99941501 - Disclosure - Stock-Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureStockBasedCompensationDetails</Role>
      <ShortName>Stock-Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureStockBasedCompensationTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>99941502 - Disclosure - Stock-Based Compensation - Stock-based compensation included in general and administrative expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureStockBasedCompensationStockBasedCompensationIncludedInGeneralAndAdministrativeExpensesDetails</Role>
      <ShortName>Stock-Based Compensation - Stock-based compensation included in general and administrative expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="ftco-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>99941601 - Disclosure - Shareholders' Equity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fortitudegold.com/role/DisclosureShareholdersEquityDetails</Role>
      <ShortName>Shareholders' Equity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.fortitudegold.com/role/DisclosureShareholdersEquity</ParentRole>
      <Position>61</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>ftco-20260331.xsd</File>
    <File>ftco-20260331_cal.xml</File>
    <File>ftco-20260331_def.xml</File>
    <File>ftco-20260331_lab.xml</File>
    <File>ftco-20260331_pre.xml</File>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="ftco-20260331x10q.htm">ftco-20260331x10q.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="349">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
