<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.20.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>933</ContextCount>
  <ElementCount>596</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>215</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Consolidated Statements of Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConsolidatedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002000 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002501 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Consolidated Statements of Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConsolidatedStatementsOfEquity</Role>
      <ShortName>Consolidated Statements of Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004000 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Conservatorship and Related Matters</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConservatorshipAndRelatedMatters</Role>
      <ShortName>Conservatorship and Related Matters</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Securitization Activities and Consolidation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SecuritizationActivitiesAndConsolidation</Role>
      <ShortName>Securitization Activities and Consolidation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Mortgage Loans and Loan Loss Reserves</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReserves</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Guarantees and Other Off-Balance Sheet Credit Exposures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/GuaranteesAndOtherOffBalanceSheetCreditExposures</Role>
      <ShortName>Guarantees and Other Off-Balance Sheet Credit Exposures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Credit Enhancements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CreditEnhancements</Role>
      <ShortName>Credit Enhancements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Investment Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecurities</Role>
      <ShortName>Investment Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Derivatives</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/Derivatives</Role>
      <ShortName>Derivatives</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Collateral and Offsetting of Assets and Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilities</Role>
      <ShortName>Collateral and Offsetting of Assets and Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Stockholders' Equity and Earnings per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShare</Role>
      <ShortName>Stockholders' Equity and Earnings per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Concentration of Credit and Other Risks</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisks</Role>
      <ShortName>Concentration of Credit and Other Risks</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Fair Value Disclosures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosures</Role>
      <ShortName>Fair Value Disclosures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - Legal Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/LegalContingencies</Role>
      <ShortName>Legal Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - Regulatory Capital</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/RegulatoryCapital</Role>
      <ShortName>Regulatory Capital</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - Selected Financial Statement Line Items</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SelectedFinancialStatementLineItems</Role>
      <ShortName>Selected Financial Statement Line Items</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2301302 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Securitization Activities and Consolidation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SecuritizationActivitiesAndConsolidationTables</Role>
      <ShortName>Securitization Activities and Consolidation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/SecuritizationActivitiesAndConsolidation</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Mortgage Loans and Loan Loss Reserves (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesTables</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReserves</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Guarantees and Other Off-Balance Sheet Credit Exposures (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/GuaranteesAndOtherOffBalanceSheetCreditExposuresTables</Role>
      <ShortName>Guarantees and Other Off-Balance Sheet Credit Exposures (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/GuaranteesAndOtherOffBalanceSheetCreditExposures</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2306302 - Disclosure - Credit Enhancements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CreditEnhancementsTables</Role>
      <ShortName>Credit Enhancements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/CreditEnhancements</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Investment Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecuritiesTables</Role>
      <ShortName>Investment Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/InvestmentSecurities</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/Debt</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Derivatives (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DerivativesTables</Role>
      <ShortName>Derivatives (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/Derivatives</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Collateral and Offsetting of Assets and Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilitiesTables</Role>
      <ShortName>Collateral and Offsetting of Assets and Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilities</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Stockholders' Equity and Earnings per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShareTables</Role>
      <ShortName>Stockholders' Equity and Earnings per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShare</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Segment Reporting (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SegmentReportingTables</Role>
      <ShortName>Segment Reporting (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/SegmentReporting</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Concentration of Credit and Other Risks (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksTables</Role>
      <ShortName>Concentration of Credit and Other Risks (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisks</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - Fair Value Disclosures (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresTables</Role>
      <ShortName>Fair Value Disclosures (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/FairValueDisclosures</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2317301 - Disclosure - Regulatory Capital (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/RegulatoryCapitalTables</Role>
      <ShortName>Regulatory Capital (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/RegulatoryCapital</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2318301 - Disclosure - Selected Financial Statement Line Items (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SelectedFinancialStatementLineItemsTables</Role>
      <ShortName>Selected Financial Statement Line Items (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/SelectedFinancialStatementLineItems</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2401403 - Disclosure - Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/SummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2401404 - Disclosure - CECL Transition Impact (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CeclTransitionImpactDetails</Role>
      <ShortName>CECL Transition Impact (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2402401 - Disclosure - Conservatorship and Related Matters (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConservatorshipAndRelatedMattersDetails</Role>
      <ShortName>Conservatorship and Related Matters (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/ConservatorshipAndRelatedMatters</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Securitization Activities and Consolidation - Consolidated VIEs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SecuritizationActivitiesAndConsolidationConsolidatedViesDetails</Role>
      <ShortName>Securitization Activities and Consolidation - Consolidated VIEs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Securitization Activities and Consolidation - Non-Consolidated VIEs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SecuritizationActivitiesAndConsolidationNonConsolidatedViesDetails</Role>
      <ShortName>Securitization Activities and Consolidation - Non-Consolidated VIEs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Mortgage Loans and Loan Loss Reserves (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Mortgage Loans and Loan Loss Reserves - Mortgage Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesMortgageLoansDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Mortgage Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Mortgage Loans and Loan Loss Reserves - Loans Purchased, Reclassified from Held-for-Investment to Held-for-Sale and Sold (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesLoansPurchasedReclassifiedFromHeldForInvestmentToHeldForSaleAndSoldDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Loans Purchased, Reclassified from Held-for-Investment to Held-for-Sale and Sold (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Mortgage Loans and Loan Loss Reserves Mortgage Loans and Loan Loss Reserves - Loan Reclassifications (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesMortgageLoansAndLoanLossReservesLoanReclassificationsDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves Mortgage Loans and Loan Loss Reserves - Loan Reclassifications (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2404406 - Disclosure - Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Held-for-Investment Loans on Nonaccrual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesAmortizedCostBasisOfHeldForInvestmentLoansOnNonaccrualDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Held-for-Investment Loans on Nonaccrual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2404407 - Disclosure - Mortgage Loans and Loan Loss Reserves Mortgage Loans and Loan Loss Reserves - Accrued Interest Receivable and Related Charge-Offs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesMortgageLoansAndLoanLossReservesAccruedInterestReceivableAndRelatedChargeOffsDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves Mortgage Loans and Loan Loss Reserves - Accrued Interest Receivable and Related Charge-Offs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2404408 - Disclosure - Mortgage Loans and Loan Loss Reserves - Detail of Allowance for Credit Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesDetailOfAllowanceForCreditLossesDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Detail of Allowance for Credit Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2404409 - Disclosure - Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Single-Family Held-for-Investment Loans by Current LTV Ratios and Vintage (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesAmortizedCostBasisOfSingleFamilyHeldForInvestmentLoansByCurrentLtvRatiosAndVintageDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Single-Family Held-for-Investment Loans by Current LTV Ratios and Vintage (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2404410 - Disclosure - Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Multifamily Held-for-Investment Loans by Credit Quality Indicator by Vintage (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesAmortizedCostBasisOfMultifamilyHeldForInvestmentLoansByCreditQualityIndicatorByVintageDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Multifamily Held-for-Investment Loans by Credit Quality Indicator by Vintage (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2404411 - Disclosure - Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Held-for-Investment Loans by Payment Status (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesAmortizedCostBasisOfHeldForInvestmentLoansByPaymentStatusDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Amortized Cost Basis of Held-for-Investment Loans by Payment Status (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2404412 - Disclosure - Mortgage Loans and Loan Loss Reserves - TDR Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesTdrActivityDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - TDR Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2404413 - Disclosure - Mortgage Loans and Loan Loss Reserves - Payment Defaults of Completed TDR Modifications (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesPaymentDefaultsOfCompletedTdrModificationsDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Payment Defaults of Completed TDR Modifications (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2404414 - Disclosure - Mortgage Loans and Loan Loss Reserves - Net Investment in Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesNetInvestmentInLoansDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Net Investment in Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2404415 - Disclosure - Mortgage Loans and Loan Loss Reserves - Individually Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesIndividuallyImpairedLoansDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Individually Impaired Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2404416 - Disclosure - Mortgage Loans and Loan Loss Reserves - Delinquency Rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/MortgageLoansAndLoanLossReservesDelinquencyRatesDetails</Role>
      <ShortName>Mortgage Loans and Loan Loss Reserves - Delinquency Rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Guarantees and Other Off-Balance Sheet Credit Exposures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/GuaranteesAndOtherOffBalanceSheetCreditExposuresDetails</Role>
      <ShortName>Guarantees and Other Off-Balance Sheet Credit Exposures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/GuaranteesAndOtherOffBalanceSheetCreditExposuresTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2405403 - Disclosure - Financial Guarantees (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FinancialGuaranteesDetails</Role>
      <ShortName>Financial Guarantees (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2405404 - Disclosure - UPB of Unconsolidated Loans by Payment Status (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/UpbOfUnconsolidatedLoansByPaymentStatusDetails</Role>
      <ShortName>UPB of Unconsolidated Loans by Payment Status (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2406401 - Disclosure - Credit Enhancements Credit Enhancements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CreditEnhancementsCreditEnhancementsDetails</Role>
      <ShortName>Credit Enhancements Credit Enhancements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2406403 - Disclosure - Credit Enhancements - Components of Credit Enhancements, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CreditEnhancementsComponentsOfCreditEnhancementsNetDetails</Role>
      <ShortName>Credit Enhancements - Components of Credit Enhancements, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2406404 - Disclosure - Credit Enhancements - Single Family Credit Enhancements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CreditEnhancementsSingleFamilyCreditEnhancementsDetails</Role>
      <ShortName>Credit Enhancements - Single Family Credit Enhancements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2406405 - Disclosure - Credit Enhancements -Multifamily Credit Enhancements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CreditEnhancementsMultifamilyCreditEnhancementsDetails</Role>
      <ShortName>Credit Enhancements -Multifamily Credit Enhancements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Investment Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecuritiesDetails</Role>
      <ShortName>Investment Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - Investment Securities - Investment Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecuritiesInvestmentSecuritiesDetails</Role>
      <ShortName>Investment Securities - Investment Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2407404 - Disclosure - Investment Securities - Trading Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecuritiesTradingSecuritiesDetails</Role>
      <ShortName>Investment Securities - Trading Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2407405 - Disclosure - Investment Securities - Available-For-Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecuritiesAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Investment Securities - Available-For-Sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2407406 - Disclosure - Investment Securities - Available-For-Sale Securities in a Gross Unrealized Loss Position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecuritiesAvailableForSaleSecuritiesInGrossUnrealizedLossPositionDetails</Role>
      <ShortName>Investment Securities - Available-For-Sale Securities in a Gross Unrealized Loss Position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>2407407 - Disclosure - Investment Securities - Gross Realized Gains and Gross Realized Losses on Sales of Available-For-Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/InvestmentSecuritiesGrossRealizedGainsAndGrossRealizedLossesOnSalesOfAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Investment Securities - Gross Realized Gains and Gross Realized Losses on Sales of Available-For-Sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Debt Text (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DebtTextDetails</Role>
      <ShortName>Debt Text (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Debt - Total Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DebtTotalDebtDetails</Role>
      <ShortName>Debt - Total Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>2408404 - Disclosure - Debt - Debt Securities of Consolidated Trusts Held by Third Parties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DebtDebtSecuritiesOfConsolidatedTrustsHeldByThirdPartiesDetails</Role>
      <ShortName>Debt - Debt Securities of Consolidated Trusts Held by Third Parties (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>2408405 - Disclosure - Debt - Other Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DebtOtherDebtDetails</Role>
      <ShortName>Debt - Other Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Derivatives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DerivativesDetails</Role>
      <ShortName>Derivatives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/DerivativesTables</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Derivatives - Derivative Assets and Liabilities at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DerivativesDerivativeAssetsAndLiabilitiesAtFairValueDetails</Role>
      <ShortName>Derivatives - Derivative Assets and Liabilities at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - Derivatives - Derivative Gains and Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DerivativesDerivativeGainsAndLossesDetails</Role>
      <ShortName>Derivatives - Derivative Gains and Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>2409405 - Disclosure - Derivatives Derivatives - Gains and Losses on Fair Value Hedge (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DerivativesDerivativesGainsAndLossesOnFairValueHedgeDetails</Role>
      <ShortName>Derivatives Derivatives - Gains and Losses on Fair Value Hedge (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>2409406 - Disclosure - Derivatives Derivatives - Cumulative Basis Adjustment due to Fair Value Hedges (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/DerivativesDerivativesCumulativeBasisAdjustmentDueToFairValueHedgesDetails</Role>
      <ShortName>Derivatives Derivatives - Cumulative Basis Adjustment due to Fair Value Hedges (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Collateral and Offsetting of Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilitiesDetails</Role>
      <ShortName>Collateral and Offsetting of Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilitiesTables</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Collateral and Offsetting of Assets and Liabilities - Offsetting of Financial Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilitiesOffsettingOfFinancialAssetsDetails</Role>
      <ShortName>Collateral and Offsetting of Assets and Liabilities - Offsetting of Financial Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>2410404 - Disclosure - Collateral and Offsetting of Assets and Liabilities - Offsetting of Financial Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilitiesOffsettingOfFinancialLiabilitiesDetails</Role>
      <ShortName>Collateral and Offsetting of Assets and Liabilities - Offsetting of Financial Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - Collateral and Offsetting of Assets and Liabilities - Collateral in the Form of Securities Pledged (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilitiesCollateralInFormOfSecuritiesPledgedDetails</Role>
      <ShortName>Collateral and Offsetting of Assets and Liabilities - Collateral in the Form of Securities Pledged (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>2410406 - Disclosure - Collateral and Offsetting of Assets and Liabilities - Underlying Collateral Pledged (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/CollateralAndOffsettingOfAssetsAndLiabilitiesUnderlyingCollateralPledgedDetails</Role>
      <ShortName>Collateral and Offsetting of Assets and Liabilities - Underlying Collateral Pledged (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Stockholders' Equity and Earnings per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShareDetails</Role>
      <ShortName>Stockholders' Equity and Earnings per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShareTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Stockholders' Equity and Earnings per Share - Changes in AOCI by Component, Net of Tax (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShareChangesInAociByComponentNetOfTaxDetails</Role>
      <ShortName>Stockholders' Equity and Earnings per Share - Changes in AOCI by Component, Net of Tax (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - Stockholders' Equity and Earnings per Share - Reclassifications from AOCI to Net Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShareReclassificationsFromAociToNetIncomeDetails</Role>
      <ShortName>Stockholders' Equity and Earnings per Share - Reclassifications from AOCI to Net Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>2411405 - Disclosure - Stockholders' Equity and Earnings per Share - Senior Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/StockholdersEquityAndEarningsPerShareSeniorPreferredStockDetails</Role>
      <ShortName>Stockholders' Equity and Earnings per Share - Senior Preferred Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/IncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/IncomeTaxes</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Segment Reporting (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SegmentReportingDetails</Role>
      <ShortName>Segment Reporting (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/SegmentReportingTables</ParentRole>
      <Position>93</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - Segment Reporting - Segment Earnings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SegmentReportingSegmentEarningsDetails</Role>
      <ShortName>Segment Reporting - Segment Earnings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>2413404 - Disclosure - Segment Reporting - Segment Earnings and Reconciliation to GAAP Condensed Consolidated Statements of Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SegmentReportingSegmentEarningsAndReconciliationToGaapCondensedConsolidatedStatementsOfComprehensiveIncomeDetails</Role>
      <ShortName>Segment Reporting - Segment Earnings and Reconciliation to GAAP Condensed Consolidated Statements of Comprehensive Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Concentration of Credit and Other Risks (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksDetails</Role>
      <ShortName>Concentration of Credit and Other Risks (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksTables</ParentRole>
      <Position>96</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Concentration of Credit and Other Risks - Concentration of Credit Risk - Single-Family Credit Guarantee Portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksConcentrationOfCreditRiskSingleFamilyCreditGuaranteePortfolioDetails</Role>
      <ShortName>Concentration of Credit and Other Risks - Concentration of Credit Risk - Single-Family Credit Guarantee Portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>2414404 - Disclosure - Concentration of Credit and Other Risks - Certain Higher-Risk Categories in the Single-Family Credit Guarantee Portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksCertainHigherRiskCategoriesInSingleFamilyCreditGuaranteePortfolioDetails</Role>
      <ShortName>Concentration of Credit and Other Risks - Certain Higher-Risk Categories in the Single-Family Credit Guarantee Portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>2414406 - Disclosure - Concentration of Credit and Other Risks - Seller Concentration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksSellerConcentrationDetails</Role>
      <ShortName>Concentration of Credit and Other Risks - Seller Concentration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>2414407 - Disclosure - Concentration of Credit and Other Risks - Servicer Concentration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksServicerConcentrationDetails</Role>
      <ShortName>Concentration of Credit and Other Risks - Servicer Concentration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>2414408 - Disclosure - Concentration of Credit and Other Risks - Mortgage Insurer Concentration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/ConcentrationOfCreditAndOtherRisksMortgageInsurerConcentrationDetails</Role>
      <ShortName>Concentration of Credit and Other Risks - Mortgage Insurer Concentration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails</Role>
      <ShortName>Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>2415403 - Disclosure - Fair Value Disclosures - Fair Value Measurements of Assets and Liabilities Using Significant Unobservable Inputs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresFairValueMeasurementsOfAssetsAndLiabilitiesUsingSignificantUnobservableInputsDetails</Role>
      <ShortName>Fair Value Disclosures - Fair Value Measurements of Assets and Liabilities Using Significant Unobservable Inputs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>2415404 - Disclosure - Fair Value Disclosures - Quantitative Information about Recurring Level 3 Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresQuantitativeInformationAboutRecurringLevel3FairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Disclosures - Quantitative Information about Recurring Level 3 Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>104</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>2415405 - Disclosure - Fair Value Disclosures - Assets Measured at Fair Value on a Non-Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresAssetsMeasuredAtFairValueOnNonRecurringBasisDetails</Role>
      <ShortName>Fair Value Disclosures - Assets Measured at Fair Value on a Non-Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>105</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>2415406 - Disclosure - Fair Value Disclosures - Fair Value Assets Measured on Nonrecurring Basis Valuation Techniques (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresFairValueAssetsMeasuredOnNonrecurringBasisValuationTechniquesDetails</Role>
      <ShortName>Fair Value Disclosures - Fair Value Assets Measured on Nonrecurring Basis Valuation Techniques (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>106</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>2415407 - Disclosure - Fair Value Disclosures - Fair Value of Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresFairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Disclosures - Fair Value of Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>107</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>2415408 - Disclosure - Fair Value Disclosures - Difference between Fair Value and UPB for Certain Financial Instruments with Fair Value Option Elected (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresDifferenceBetweenFairValueAndUpbForCertainFinancialInstrumentsWithFairValueOptionElectedDetails</Role>
      <ShortName>Fair Value Disclosures - Difference between Fair Value and UPB for Certain Financial Instruments with Fair Value Option Elected (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>108</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>2415409 - Disclosure - Fair Value Disclosures Fair Value Disclosures - Changes in Fair Value under the FVO option (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/FairValueDisclosuresFairValueDisclosuresChangesInFairValueUnderFvoOptionDetails</Role>
      <ShortName>Fair Value Disclosures Fair Value Disclosures - Changes in Fair Value under the FVO option (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>2416401 - Disclosure - Legal Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/LegalContingenciesDetails</Role>
      <ShortName>Legal Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.freddiemac.com/role/LegalContingencies</ParentRole>
      <Position>110</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>2417403 - Disclosure - Regulatory Capital Regulatory Capital - Net Worth and Minimum Capital (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/RegulatoryCapitalRegulatoryCapitalNetWorthAndMinimumCapitalDetails</Role>
      <ShortName>Regulatory Capital Regulatory Capital - Net Worth and Minimum Capital (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>111</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>2418403 - Disclosure - Selected Financial Statement Line Items - Significant Components of Other Assets and Other Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SelectedFinancialStatementLineItemsSignificantComponentsOfOtherAssetsAndOtherLiabilitiesDetails</Role>
      <ShortName>Selected Financial Statement Line Items - Significant Components of Other Assets and Other Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>112</Position>
    </Report>
    <Report instance="a20201q10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>2418404 - Disclosure - Selected Financial Statement Line Items Selected Financial Statement Line Items - Components of Investment Gains (Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.freddiemac.com/role/SelectedFinancialStatementLineItemsSelectedFinancialStatementLineItemsComponentsOfInvestmentGainsLossesDetails</Role>
      <ShortName>Selected Financial Statement Line Items Selected Financial Statement Line Items - Components of Investment Gains (Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>113</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="a20201q10q.htm">a20201q10q.htm</File>
    <File>a1q2010qex311.htm</File>
    <File>a1q2010qex312.htm</File>
    <File>a1q2010qex321.htm</File>
    <File>a1q2010qex322.htm</File>
    <File>a1q2010qex41.htm</File>
    <File>fmcc-20200331.xsd</File>
    <File>fmcc-20200331_cal.xml</File>
    <File>fmcc-20200331_def.xml</File>
    <File>fmcc-20200331_lab.xml</File>
    <File>fmcc-20200331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>chart-057f3101cc875bc8b78.jpg</File>
    <File>chart-0c0121ff5f8977cf12b.jpg</File>
    <File>chart-0eedc9f0b60d5358974.jpg</File>
    <File>chart-140213d63cc7e21f7e6.jpg</File>
    <File>chart-146427389807259bbb5.jpg</File>
    <File>chart-242376067c1d5a71b1a.jpg</File>
    <File>chart-328ab47f98c7d121106.jpg</File>
    <File>chart-386acf3195294a9de03.jpg</File>
    <File>chart-3c0c06ac70835a836e1.jpg</File>
    <File>chart-493935faeee75c4aae9.jpg</File>
    <File>chart-4b076c9965c7eb0e4b0.jpg</File>
    <File>chart-522a294dc012cd44000.jpg</File>
    <File>chart-5270a91ca5f2043ccd7.jpg</File>
    <File>chart-52792d9ecd74f920d4b.jpg</File>
    <File>chart-54b2f9158d925de3b65.jpg</File>
    <File>chart-5d02c7a81e3cee922cc.jpg</File>
    <File>chart-5f91d48be276593aa81.jpg</File>
    <File>chart-6f4b7467bc6a5e3b97a.jpg</File>
    <File>chart-6f7160c8a266e3377ec.jpg</File>
    <File>chart-7373add2918811fbcfc.jpg</File>
    <File>chart-786fd0a4286a4143ebe.jpg</File>
    <File>chart-8596f1aa07d2dfb50a7.jpg</File>
    <File>chart-910bd55cabdbfb8a522.jpg</File>
    <File>chart-9445186e75b0e5ae790.jpg</File>
    <File>chart-951636b7ac6f5c9da3e.jpg</File>
    <File>chart-9aa87195141345a1641.jpg</File>
    <File>chart-a15ebb4b77f45a1f962.jpg</File>
    <File>chart-a92e7c6f65ca4a30e20.jpg</File>
    <File>chart-aa8cf8e927f48841bab.jpg</File>
    <File>chart-abd3ced681c9a60a71a.jpg</File>
    <File>chart-af1ad1de21985c8d900.jpg</File>
    <File>chart-b1da0260ed655915950.jpg</File>
    <File>chart-be1da8f3cc8e5b118ca.jpg</File>
    <File>chart-bf8ee2b2c760a70646a.jpg</File>
    <File>chart-c3f6c1c585fe2ec061e.jpg</File>
    <File>chart-cc07a28768e8030e726.jpg</File>
    <File>chart-db9619f3d5df55a188c.jpg</File>
    <File>chart-ea2be20afe056580bc7.jpg</File>
    <File>chart-fb4d500877c21da1aba.jpg</File>
    <File>primarylogoa04.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.sec.gov/stpr/2018-01-31</BaseTaxonomy>
    <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>
