<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.24.3</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>1133</ContextCount>
  <ElementCount>337</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>134</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Consolidated Statements of Assets and Liabilities (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedStatementsOfAssetsAndLiabilitiesUnaudited</Role>
      <ShortName>Consolidated Statements of Assets and Liabilities (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100030 - Statement - Consolidated Statements of Assets and Liabilities (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedStatementsOfAssetsAndLiabilitiesUnauditedParenthetical</Role>
      <ShortName>Consolidated Statements of Assets and Liabilities (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100040 - Statement - Consolidated Statement of Operations (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedStatementOfOperationsUnaudited</Role>
      <ShortName>Consolidated Statement of Operations (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100050 - Statement - Consolidated Statement of Changes in Net Assets (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedStatementOfChangesInNetAssetsUnaudited</Role>
      <ShortName>Consolidated Statement of Changes in Net Assets (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100060 - Statement - Consolidated Statement of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedStatementOfCashFlowsUnaudited</Role>
      <ShortName>Consolidated Statement of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100070 - Statement - Consolidated Schedule of Investments (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsUnaudited</Role>
      <ShortName>Consolidated Schedule of Investments (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100080 - Statement - Consolidated Schedule of Investments (Unaudited) (Derivatives)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsUnauditedDerivatives</Role>
      <ShortName>Consolidated Schedule of Investments (Unaudited) (Derivatives)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100090 - Statement - Consolidated Schedule of Investments (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsUnauditedParenthetical2</Role>
      <ShortName>Consolidated Schedule of Investments (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100100 - Statement - Consolidated Schedule of Investments (Unaudited) ( Unfunded Commitments)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsUnauditedUnfundedCommitments</Role>
      <ShortName>Consolidated Schedule of Investments (Unaudited) ( Unfunded Commitments)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995447 - Disclosure - Insider Trading Policies and Procedures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc</Role>
      <ShortName>Insider Trading Policies and Procedures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995457 - Disclosure - Organization</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureOrganization</Role>
      <ShortName>Organization</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995467 - Disclosure - Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureSignificantAccountingPolicies1</Role>
      <ShortName>Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995477 - Disclosure - Agreements and Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureAgreementsAndRelatedPartyTransactions</Role>
      <ShortName>Agreements and Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995487 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureInvestments</Role>
      <ShortName>Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995497 - Disclosure - Derivative Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureDerivativeInstruments</Role>
      <ShortName>Derivative Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995507 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995517 - Disclosure - Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureBorrowings</Role>
      <ShortName>Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995527 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureCommitmentsAndContingencies1</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995537 - Disclosure - Net Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureNetAssets1</Role>
      <ShortName>Net Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995547 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureEarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995557 - Disclosure - Financial Highlights</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFinancialHighlights1</Role>
      <ShortName>Financial Highlights</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995567 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995577 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureSignificantAccountingPolicies1</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995587 - Disclosure - Agreements and Related Party Transactions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureAgreementsAndRelatedPartyTransactionsTables</Role>
      <ShortName>Agreements and Related Party Transactions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureAgreementsAndRelatedPartyTransactions</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995597 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureInvestmentsTables</Role>
      <ShortName>Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureInvestments</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995607 - Disclosure - Derivative Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureDerivativeInstrumentsTables</Role>
      <ShortName>Derivative Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureDerivativeInstruments</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995617 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995627 - Disclosure - Borrowings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureBorrowingsTables</Role>
      <ShortName>Borrowings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureBorrowings</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995637 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureCommitmentsAndContingencies1</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995647 - Disclosure - Net Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureNetAssetsTables</Role>
      <ShortName>Net Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureNetAssets1</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995657 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureEarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureEarningsPerShare</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995667 - Disclosure - Financial Highlights (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFinancialHighlightsTables</Role>
      <ShortName>Financial Highlights (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFinancialHighlights1</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995677 - Disclosure - Organization - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureOrganizationAdditionalInformationDetails</Role>
      <ShortName>Organization - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995687 - Disclosure - Significant Accounting Policies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureSignificantAccountingPoliciesAdditionalInformationDetails</Role>
      <ShortName>Significant Accounting Policies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995697 - Disclosure - Agreements and Related Party Transactions - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureAgreementsAndRelatedPartyTransactionsAdditionalInformationDetails</Role>
      <ShortName>Agreements and Related Party Transactions - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995707 - Disclosure - Agreements and Related Party Transactions - Schedule of Related Party Fees, Expenses and Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureAgreementsAndRelatedPartyTransactionsScheduleOfRelatedPartyFeesExpensesAndTransactionsDetails</Role>
      <ShortName>Agreements and Related Party Transactions - Schedule of Related Party Fees, Expenses and Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995717 - Disclosure - Investments - Schedule of Investment Portfolio at Amortized Cost and Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureInvestmentsScheduleOfInvestmentPortfolioAtAmortizedCostAndFairValueDetails</Role>
      <ShortName>Investments - Schedule of Investment Portfolio at Amortized Cost and Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995727 - Disclosure - Investments - Schedule of Industry Composition of Investments at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureInvestmentsScheduleOfIndustryCompositionOfInvestmentsAtFairValueDetails</Role>
      <ShortName>Investments - Schedule of Industry Composition of Investments at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995737 - Disclosure - Investments - Schedule of Geographic Composition of Investments at Cost and Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureInvestmentsScheduleOfGeographicCompositionOfInvestmentsAtCostAndFairValueDetails</Role>
      <ShortName>Investments - Schedule of Geographic Composition of Investments at Cost and Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995747 - Disclosure - Investments - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureInvestmentsAdditionalInformationDetails</Role>
      <ShortName>Investments - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995757 - Disclosure - Derivative Instruments - Schedule of Open Foreign Currency Forward Contracts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureDerivativeInstrumentsScheduleOfOpenForeignCurrencyForwardContractsDetails</Role>
      <ShortName>Derivative Instruments - Schedule of Open Foreign Currency Forward Contracts (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995767 - Disclosure - Derivative Instruments - Schedule of Net Realized and Unrealized Gains and Losses on Derivative Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureDerivativeInstrumentsScheduleOfNetRealizedAndUnrealizedGainsAndLossesOnDerivativeInstrumentsDetails</Role>
      <ShortName>Derivative Instruments - Schedule of Net Realized and Unrealized Gains and Losses on Derivative Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995787 - Disclosure - Derivative Instruments - Derivative Assets and Liabilities by Counterparty, Net of Amounts Available for Offset Under Master Netting Agreement or Similar Arrangement, and Net of Related Collateral Received for Assets or Pledged for Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureDerivativeInstrumentsDerivativeAssetsAndLiabilitiesByCounterpartyNetOfAmountsAvailableForOffsetUnderMasterNettingAgreementOrSimi</Role>
      <ShortName>Derivative Instruments - Derivative Assets and Liabilities by Counterparty, Net of Amounts Available for Offset Under Master Netting Agreement or Similar Arrangement, and Net of Related Collateral Received for Assets or Pledged for Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>995797 - Disclosure - Fair Value Measurements - Summary of Fair Value Hierarchy of Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfFairValueHierarchyOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Measurements - Summary of Fair Value Hierarchy of Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>995807 - Disclosure - Fair Value Measurements - Summary of Changes in Fair Value of Financial Instruments for which Level 3 Inputs were used to Determine Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfChangesInFairValueOfFinancialInstrumentsForWhichLevel3InputsWereUsedToDetermineFairValueDetail</Role>
      <ShortName>Fair Value Measurements - Summary of Changes in Fair Value of Financial Instruments for which Level 3 Inputs were used to Determine Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>995817 - Disclosure - Fair Value Measurements - Summary of Changes in Fair Value of Financial Instruments for which Level 3 Inputs were used to Determine Fair Value (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfChangesInFairValueOfFinancialInstrumentsForWhichLevel3InputsWereUsedToDetermineFairValueParent</Role>
      <ShortName>Fair Value Measurements - Summary of Changes in Fair Value of Financial Instruments for which Level 3 Inputs were used to Determine Fair Value (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>995827 - Disclosure - Fair Value Measurements - Summary of Quantitative Information about Significant Unobservable Inputs of Level 3 financial instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfQuantitativeInformationAboutSignificantUnobservableInputsOfLevel3FinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Measurements - Summary of Quantitative Information about Significant Unobservable Inputs of Level 3 financial instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>995837 - Disclosure - Fair Value Measurements - Summary of Quantitative Information about Significant Unobservable Inputs of Level 3 financial instruments (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfQuantitativeInformationAboutSignificantUnobservableInputsOfLevel3FinancialInstrumentsParentheticalDe</Role>
      <ShortName>Fair Value Measurements - Summary of Quantitative Information about Significant Unobservable Inputs of Level 3 financial instruments (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>995847 - Disclosure - Borrowings - Schedule of Outstanding Debt Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureBorrowingsScheduleOfOutstandingDebtObligationsDetails</Role>
      <ShortName>Borrowings - Schedule of Outstanding Debt Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>995857 - Disclosure - Borrowings - Schedule of Outstanding Debt Obligations (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureBorrowingsScheduleOfOutstandingDebtObligationsParentheticalDetails</Role>
      <ShortName>Borrowings - Schedule of Outstanding Debt Obligations (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>995867 - Disclosure - Borrowings - Summary of Supplemental Cash Flow Information Relating to Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureBorrowingsSummaryOfSupplementalCashFlowInformationRelatingToLeasesDetails</Role>
      <ShortName>Borrowings - Summary of Supplemental Cash Flow Information Relating to Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>995877 - Disclosure - Borrowings - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureBorrowingsAdditionalInformationDetails</Role>
      <ShortName>Borrowings - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>995887 - Disclosure - Commitments and Contingencies - Summary of Unfunded Commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureCommitmentsAndContingenciesSummaryOfUnfundedCommitmentsDetails</Role>
      <ShortName>Commitments and Contingencies - Summary of Unfunded Commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>995897 - Disclosure - Net Assets - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureNetAssetsAdditionalInformationDetails</Role>
      <ShortName>Net Assets - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>995907 - Disclosure - Net Assets - Summary of Total Shares Issued and Aggregate Offering Proceeds Related to Capital Drawdowns Delivered (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureNetAssetsSummaryOfTotalSharesIssuedAndAggregateOfferingProceedsRelatedToCapitalDrawdownsDeliveredDetails</Role>
      <ShortName>Net Assets - Summary of Total Shares Issued and Aggregate Offering Proceeds Related to Capital Drawdowns Delivered (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>995917 - Disclosure - Net Assets - Summary of Distributions Declared (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureNetAssetsSummaryOfDistributionsDeclaredDetails</Role>
      <ShortName>Net Assets - Summary of Distributions Declared (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>995927 - Disclosure - Net Assets - Summary of Dividend Reinvestment Plan Shares Issued to Shareholders and Value of Such Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureNetAssetsSummaryOfDividendReinvestmentPlanSharesIssuedToShareholdersAndValueOfSuchSharesDetails</Role>
      <ShortName>Net Assets - Summary of Dividend Reinvestment Plan Shares Issued to Shareholders and Value of Such Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>995937 - Disclosure - Earnings Per Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureEarningsPerShareScheduleOfComputationOfBasicAndDilutedEarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>995947 - Disclosure - Financial Highlights - Summary of Financial Highlights (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsDetails</Role>
      <ShortName>Financial Highlights - Summary of Financial Highlights (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>995957 - Disclosure - Financial Highlights - Summary of Financial Highlights (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsParentheticalDetails</Role>
      <ShortName>Financial Highlights - Summary of Financial Highlights (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="ck0001849894-20240930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>995967 - Disclosure - Subsequent Events - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://msdinvestmentcorp.com/20240930/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetails</Role>
      <ShortName>Subsequent Events - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</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" isDefinitelyFs="true" isUsgaap="true" original="ck0001849894-20240930.htm">ck0001849894-20240930.htm</File>
    <File>ck0001849894-20240930.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="2">http://fasb.org/srt/2024</BaseTaxonomy>
    <BaseTaxonomy items="3116">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="3">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
