<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.2.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>322</ContextCount>
  <ElementCount>368</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>74</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0000002 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>0000003 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>0000004 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF NET INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFNETINCOME</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF NET INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>0000005 - Statement - CONDENSED CONSOLIDATED STATEMETNS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CONDENSEDCONSOLIDATEDSTATEMETNSOFCOMPREHENSIVEINCOME</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMETNS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>0000006 - Statement - CONDENSED CONSOLIDATED STATEMETNS OF COMPREHENSIVE INCOME (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CONDENSEDCONSOLIDATEDSTATEMETNSOFCOMPREHENSIVEINCOMEParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMETNS OF COMPREHENSIVE INCOME (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>0000007 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>0000008 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>0000009 - Disclosure - Description of Business, Basis of Presentation and Recent Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/DescriptionofBusinessBasisofPresentationandRecentAccountingPronouncements</Role>
      <ShortName>Description of Business, Basis of Presentation and Recent Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>0000010 - Disclosure - Property and Equipment, Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/PropertyandEquipmentNet</Role>
      <ShortName>Property and Equipment, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>0000011 - Disclosure - Investments in Marketable Debt Securities, Available-for-Sale</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSale</Role>
      <ShortName>Investments in Marketable Debt Securities, Available-for-Sale</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>0000012 - Disclosure - Acquisitions, Goodwill and Other Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssets</Role>
      <ShortName>Acquisitions, Goodwill and Other Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>0000013 - Disclosure - Selected Balance Sheet Data</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetData</Role>
      <ShortName>Selected Balance Sheet Data</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>0000014 - Disclosure - Related-Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/RelatedPartyTransactions</Role>
      <ShortName>Related-Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>0000015 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>0000016 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>0000017 - Disclosure - Stock-Based Compensation Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlans</Role>
      <ShortName>Stock-Based Compensation Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>0000018 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>0000019 - Disclosure - Earnings per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/EarningsperShare</Role>
      <ShortName>Earnings per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>0000020 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CommitmentsandContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>0000021 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>0000022 - Disclosure - Description of Business, Basis of Presentation and Recent Accounting Pronouncements (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/DescriptionofBusinessBasisofPresentationandRecentAccountingPronouncementsPolicies</Role>
      <ShortName>Description of Business, Basis of Presentation and Recent Accounting Pronouncements (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/DescriptionofBusinessBasisofPresentationandRecentAccountingPronouncements</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>0000023 - Disclosure - Property and Equipment, Net (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/PropertyandEquipmentNetTables</Role>
      <ShortName>Property and Equipment, Net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/PropertyandEquipmentNet</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>0000024 - Disclosure - Investments in Marketable Debt Securities, Available-for-Sale (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSaleTables</Role>
      <ShortName>Investments in Marketable Debt Securities, Available-for-Sale (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSale</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>0000025 - Disclosure - Acquisitions, Goodwill and Other Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssetsTables</Role>
      <ShortName>Acquisitions, Goodwill and Other Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssets</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>0000026 - Disclosure - Selected Balance Sheet Data (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetDataTables</Role>
      <ShortName>Selected Balance Sheet Data (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/SelectedBalanceSheetData</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>0000027 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/FairValueMeasurements</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>0000028 - Disclosure - Stock-Based Compensation Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlansTables</Role>
      <ShortName>Stock-Based Compensation Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/StockBasedCompensationPlans</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>0000029 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/IncomeTaxes</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>0000030 - Disclosure - Earnings per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/EarningsperShareTables</Role>
      <ShortName>Earnings per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/EarningsperShare</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>0000031 - Disclosure - Description of Business, Basis of Presentation and Recent Accounting Pronouncements - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/DescriptionofBusinessBasisofPresentationandRecentAccountingPronouncementsNarrativeDetail</Role>
      <ShortName>Description of Business, Basis of Presentation and Recent Accounting Pronouncements - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/DescriptionofBusinessBasisofPresentationandRecentAccountingPronouncementsPolicies</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>0000032 - Disclosure - Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetail</Role>
      <ShortName>Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>0000033 - Disclosure - Property and Equipment, Net - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/PropertyandEquipmentNetNarrativeDetail</Role>
      <ShortName>Property and Equipment, Net - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>0000034 - Disclosure - Investments in Marketable Debt Securities, Available-for-Sale - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSaleScheduleofAmortizedCostandFairValueofMarketableSecuritiesAvailableforSalebyTypeofSecurityDetail</Role>
      <ShortName>Investments in Marketable Debt Securities, Available-for-Sale - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>0000035 - Disclosure - Investments in Marketable Debt Securities, Available-for-Sale - Amortized Cost and Fair Value of Investments in Available for Sale Securities Unrealized Loss Position (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSaleAmortizedCostandFairValueofInvestmentsinAvailableforSaleSecuritiesUnrealizedLossPositionDetail</Role>
      <ShortName>Investments in Marketable Debt Securities, Available-for-Sale - Amortized Cost and Fair Value of Investments in Available for Sale Securities Unrealized Loss Position (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>0000036 - Disclosure - Investments in Marketable Debt Securities, Available-for-Sale - Gross Realized Gains and Losses from Sale of Available for Sale Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSaleGrossRealizedGainsandLossesfromSaleofAvailableforSaleSecuritiesDetail</Role>
      <ShortName>Investments in Marketable Debt Securities, Available-for-Sale - Gross Realized Gains and Losses from Sale of Available for Sale Securities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>0000037 - Disclosure - Investments in Marketable Debt Securities, Available-for-Sale - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSaleNarrativeDetail</Role>
      <ShortName>Investments in Marketable Debt Securities, Available-for-Sale - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSaleTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>0000038 - Disclosure - Investments in Marketable Debt Securities, Available-for-Sale - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Contractual Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/InvestmentsinMarketableDebtSecuritiesAvailableforSaleScheduleofAmortizedCostandFairValueofMarketableSecuritiesAvailableforSalebyContractualMaturityDetail</Role>
      <ShortName>Investments in Marketable Debt Securities, Available-for-Sale - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Contractual Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>0000039 - Disclosure - Acquisitions, Goodwill and Other Intangible Assets - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssetsNarrativeDetail</Role>
      <ShortName>Acquisitions, Goodwill and Other Intangible Assets - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssetsTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>0000040 - Disclosure - Acquisitions, Goodwill and Other Intangible Assets - Summary of Goodwill and Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssetsSummaryofGoodwillandIntangibleAssetsDetail</Role>
      <ShortName>Acquisitions, Goodwill and Other Intangible Assets - Summary of Goodwill and Intangible Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>0000041 - Disclosure - Acquisitions, Goodwill and Other Intangible Assets - Summary of Net Change in Carrying Value of Goodwill (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssetsSummaryofNetChangeinCarryingValueofGoodwillDetail</Role>
      <ShortName>Acquisitions, Goodwill and Other Intangible Assets - Summary of Net Change in Carrying Value of Goodwill (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>0000042 - Disclosure - Acquisitions, Goodwill and Other Intangible Assets - Schedule of Estimated Amortization Expense for Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/AcquisitionsGoodwillandOtherIntangibleAssetsScheduleofEstimatedAmortizationExpenseforIntangibleAssetsDetail</Role>
      <ShortName>Acquisitions, Goodwill and Other Intangible Assets - Schedule of Estimated Amortization Expense for Intangible Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>0000043 - Disclosure - Selected Balance Sheet Data - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetDataNarrativeDetail</Role>
      <ShortName>Selected Balance Sheet Data - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>0000044 - Disclosure - Selected Balance Sheet Data - Schedule of Other Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetDataScheduleofOtherAssetsDetail</Role>
      <ShortName>Selected Balance Sheet Data - Schedule of Other Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>0000045 - Disclosure - Selected Balance Sheet Data - Summary of Net Change in Carrying Value of MSRs (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetDataSummaryofNetChangeinCarryingValueofMSRsDetail</Role>
      <ShortName>Selected Balance Sheet Data - Summary of Net Change in Carrying Value of MSRs (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>0000046 - Disclosure - Selected Balance Sheet Data - Components of Deferred Compensation and Commissions (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetDataComponentsofDeferredCompensationandCommissionsDetail</Role>
      <ShortName>Selected Balance Sheet Data - Components of Deferred Compensation and Commissions (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>0000047 - Disclosure - Selected Balance Sheet Data - Summary of Net Change in Carrying Value of Assets Held in Rabbi Trust and Deferred Compensation Liability (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetDataSummaryofNetChangeinCarryingValueofAssetsHeldinRabbiTrustandDeferredCompensationLiabilityDetail</Role>
      <ShortName>Selected Balance Sheet Data - Summary of Net Change in Carrying Value of Assets Held in Rabbi Trust and Deferred Compensation Liability (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>0000048 - Disclosure - Selected Balance Sheet Data - Schedule of Other Liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SelectedBalanceSheetDataScheduleofOtherLiabilitiesDetail</Role>
      <ShortName>Selected Balance Sheet Data - Schedule of Other Liabilities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>0000049 - Disclosure - Related-Party Transactions - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/RelatedPartyTransactionsNarrativeDetail</Role>
      <ShortName>Related-Party Transactions - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>0000050 - Disclosure - Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/FairValueMeasurementsScheduleofAssetsandLiabilitiesatFairValueonRecurringBasisDetail</Role>
      <ShortName>Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>0000051 - Disclosure - Fair Value Measurements - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/FairValueMeasurementsNarrativeDetail</Role>
      <ShortName>Fair Value Measurements - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>0000052 - Disclosure - Fair Value Measurements - Schedule of Reconciliation of Contingent Consideration Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/FairValueMeasurementsScheduleofReconciliationofContingentConsiderationMeasuredatFairValueonRecurringBasisDetail</Role>
      <ShortName>Fair Value Measurements - Schedule of Reconciliation of Contingent Consideration Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>0000053 - Disclosure - Fair Value Measurements - Schedule of Fair Value Liabilities Measured On Recurring Basis Valuation Techniques (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/FairValueMeasurementsScheduleofFairValueLiabilitiesMeasuredOnRecurringBasisValuationTechniquesDetail</Role>
      <ShortName>Fair Value Measurements - Schedule of Fair Value Liabilities Measured On Recurring Basis Valuation Techniques (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>0000054 - Disclosure - Stockholders' Equity - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockholdersEquityNarrativeDetail</Role>
      <ShortName>Stockholders' Equity - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>0000055 - Disclosure - Stock-Based Compensation Plans - 2013 Omnibus Equity Incentive Plan (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlans2013OmnibusEquityIncentivePlanDetail</Role>
      <ShortName>Stock-Based Compensation Plans - 2013 Omnibus Equity Incentive Plan (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>0000056 - Disclosure - Stock-Based Compensation Plans - Awards Granted and Settled (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlansAwardsGrantedandSettledDetails</Role>
      <ShortName>Stock-Based Compensation Plans - Awards Granted and Settled (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>0000057 - Disclosure - Stock-Based Compensation Plans - Outstanding Awards Under 2013 Omnibus Equity Incentive Plan (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlansOutstandingAwardsUnder2013OmnibusEquityIncentivePlanDetail</Role>
      <ShortName>Stock-Based Compensation Plans - Outstanding Awards Under 2013 Omnibus Equity Incentive Plan (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>0000058 - Disclosure - Stock-Based Compensation Plans - Employee Stock Purchase Plan (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlansEmployeeStockPurchasePlanDetail</Role>
      <ShortName>Stock-Based Compensation Plans - Employee Stock Purchase Plan (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>0000059 - Disclosure - Stock-Based Compensation Plans - SARs and DSUs (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlansSARsandDSUsDetail</Role>
      <ShortName>Stock-Based Compensation Plans - SARs and DSUs (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>0000060 - Disclosure - Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/StockBasedCompensationPlansStockBasedCompensationExpenseDetail</Role>
      <ShortName>Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>0000061 - Disclosure - Income Taxes - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/IncomeTaxesNarrativeDetail</Role>
      <ShortName>Income Taxes - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>0000062 - Disclosure - Income Taxes - Components of Provision for Income Taxes and Income before Provision for Income Taxes (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/IncomeTaxesComponentsofProvisionforIncomeTaxesandIncomebeforeProvisionforIncomeTaxesDetail</Role>
      <ShortName>Income Taxes - Components of Provision for Income Taxes and Income before Provision for Income Taxes (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>0000063 - Disclosure - Earnings per Share - Computation of Basic and Diluted Earnings Per Share, Including Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/EarningsperShareComputationofBasicandDilutedEarningsPerShareIncludingAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetail</Role>
      <ShortName>Earnings per Share - Computation of Basic and Diluted Earnings Per Share, Including Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>0000064 - Disclosure - Commitments and Contingencies - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/CommitmentsandContingenciesNarrativeDetail</Role>
      <ShortName>Commitments and Contingencies - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="mmi-20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>0000065 - Disclosure - Subsequent Events - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://marcusmillichapinc.com/role/SubsequentEventsNarrativeDetail</Role>
      <ShortName>Subsequent Events - Narrative (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 2 fact(s) appearing in ix:hidden were eligible for transformation: mmi:BusinessCombinationContingentDeferredConsiderationArrangementsEarnOutPeriod, mmi:DeferredCompensationLiabilityPayoutPeriod -  mmi-20220930.htm 4</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="mmi-20220930.htm">mmi-20220930.htm</File>
    <File>mmi-20220930.xsd</File>
    <File>mmi-20220930_cal.xml</File>
    <File>mmi-20220930_def.xml</File>
    <File>mmi-20220930_lab.xml</File>
    <File>mmi-20220930_pre.xml</File>
    <File>mmi-20220930x10qxex311.htm</File>
    <File>mmi-20220930x10qxex312.htm</File>
    <File>mmi-20220930x10qxex321.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1066">http://fasb.org/us-gaap/2022</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2022</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
