<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>215</ContextCount>
  <ElementCount>422</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>91</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0002002 - Document - Audit Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/AuditInformation</Role>
      <ShortName>Audit Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001003 - Statement - CONSOLIDATED BALANCE SHEET/CONSOLIDATED STATEMENT OF ASSETS AND LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CONSOLIDATEDBALANCESHEETCONSOLIDATEDSTATEMENTOFASSETSANDLIABILITIES</Role>
      <ShortName>CONSOLIDATED BALANCE SHEET/CONSOLIDATED STATEMENT OF ASSETS AND LIABILITIES</ShortName>
      <MenuCategory>Uncategorized</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002004 - Statement - CONSOLIDATED BALANCE SHEET/CONSOLIDATED STATEMENT OF ASSETS AND LIABILITIES (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CONSOLIDATEDBALANCESHEETCONSOLIDATEDSTATEMENTOFASSETSANDLIABILITIESParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEET/CONSOLIDATED STATEMENT OF ASSETS AND LIABILITIES (Parenthetical)</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003005 - Statement - CONSOLIDATED STATEMENT OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CONSOLIDATEDSTATEMENTOFOPERATIONS</Role>
      <ShortName>CONSOLIDATED STATEMENT OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004006 - Statement - CONSOLIDATED STATEMENT OF SHAREHOLDERS??? EQUITY/CONSOLIDATED STATEMENT OF CHANGES IN NET ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CONSOLIDATEDSTATEMENTOFSHAREHOLDERSEQUITYCONSOLIDATEDSTATEMENTOFCHANGESINNETASSETS</Role>
      <ShortName>CONSOLIDATED STATEMENT OF SHAREHOLDERS??? EQUITY/CONSOLIDATED STATEMENT OF CHANGES IN NET ASSETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1005007 - Statement - CONSOLIDATED STATEMENT OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CONSOLIDATEDSTATEMENTOFCASHFLOWS</Role>
      <ShortName>CONSOLIDATED STATEMENT OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2001008 - Disclosure - CONSOLIDATED PORTFOLIO OF INVESTMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CONSOLIDATEDPORTFOLIOOFINVESTMENTS</Role>
      <ShortName>CONSOLIDATED PORTFOLIO OF INVESTMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2102101 - Disclosure - Organization</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/Organization</Role>
      <ShortName>Organization</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2104102 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/BasisofPresentation</Role>
      <ShortName>Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2105103 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SummaryofSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2108104 - Disclosure - Recent Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/RecentAccountingPronouncements</Role>
      <ShortName>Recent Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2109105 - Disclosure - Merger with Tremont Mortgage Trust</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/MergerwithTremontMortgageTrust</Role>
      <ShortName>Merger with Tremont Mortgage Trust</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2114106 - Disclosure - Loans Held for Investment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LoansHeldforInvestment</Role>
      <ShortName>Loans Held for Investment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2121107 - Disclosure - Secured Financing Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SecuredFinancingAgreements</Role>
      <ShortName>Secured Financing Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2126108 - Disclosure - Fair Value of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/FairValueofFinancialInstruments</Role>
      <ShortName>Fair Value of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2129109 - Disclosure - Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/ShareholdersEquity</Role>
      <ShortName>Shareholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2134110 - Disclosure - Management Agreement with our Manager</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/ManagementAgreementwithourManager</Role>
      <ShortName>Management Agreement with our Manager</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2136111 - Disclosure - Related Person Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/RelatedPersonTransactions</Role>
      <ShortName>Related Person Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2138112 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2140113 - Disclosure - Weighted Average Common Shares</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/WeightedAverageCommonShares</Role>
      <ShortName>Weighted Average Common Shares</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2143114 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CommitmentsandContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2145115 - Disclosure - Legal Proceedings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LegalProceedings</Role>
      <ShortName>Legal Proceedings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2147116 - Disclosure - SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SCHEDULEIVMORTGAGELOANSONREALESTATE</Role>
      <ShortName>SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2206201 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SummaryofSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/SummaryofSignificantAccountingPolicies</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Merger with Tremont Mortgage Trust (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/MergerwithTremontMortgageTrustTables</Role>
      <ShortName>Merger with Tremont Mortgage Trust (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/MergerwithTremontMortgageTrust</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2315302 - Disclosure - Loans Held for Investment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LoansHeldforInvestmentTables</Role>
      <ShortName>Loans Held for Investment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/LoansHeldforInvestment</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2322303 - Disclosure - Secured Financing Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SecuredFinancingAgreementsTables</Role>
      <ShortName>Secured Financing Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/SecuredFinancingAgreements</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2327304 - Disclosure - Fair Value of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/FairValueofFinancialInstrumentsTables</Role>
      <ShortName>Fair Value of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/FairValueofFinancialInstruments</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2330305 - Disclosure - Shareholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/ShareholdersEquityTables</Role>
      <ShortName>Shareholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/ShareholdersEquity</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2341306 - Disclosure - Weighted Average Common Shares (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/WeightedAverageCommonSharesTables</Role>
      <ShortName>Weighted Average Common Shares (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/WeightedAverageCommonShares</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - Organization (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/OrganizationDetails</Role>
      <ShortName>Organization (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/Organization</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SummaryofSignificantAccountingPoliciesAdditionalInformationDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Merger with Tremont Mortgage Trust - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/MergerwithTremontMortgageTrustNarrativeDetails</Role>
      <ShortName>Merger with Tremont Mortgage Trust - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2412404 - Disclosure - Merger with Tremont Mortgage Trust - Summary of Consideration Transferred and Liabilities Assumed (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/MergerwithTremontMortgageTrustSummaryofConsiderationTransferredandLiabilitiesAssumedDetails</Role>
      <ShortName>Merger with Tremont Mortgage Trust - Summary of Consideration Transferred and Liabilities Assumed (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2413405 - Disclosure - Merger with Tremont Mortgage Trust- Purchase Price Allocation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/MergerwithTremontMortgageTrustPurchasePriceAllocationDetails</Role>
      <ShortName>Merger with Tremont Mortgage Trust- Purchase Price Allocation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2416406 - Disclosure - Loans Held for Investment - Loan Portfolio Statistics (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LoansHeldforInvestmentLoanPortfolioStatisticsDetails</Role>
      <ShortName>Loans Held for Investment - Loan Portfolio Statistics (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2417407 - Disclosure - Loans Held for Investment - Loan Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LoansHeldforInvestmentLoanActivityDetails</Role>
      <ShortName>Loans Held for Investment - Loan Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2418408 - Disclosure - Loans Held for Investment - Loan Portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LoansHeldforInvestmentLoanPortfolioDetails</Role>
      <ShortName>Loans Held for Investment - Loan Portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2419409 - Disclosure - Loans Held for Investment - Loan Risk Ratings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LoansHeldforInvestmentLoanRiskRatingsDetails</Role>
      <ShortName>Loans Held for Investment - Loan Risk Ratings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2420410 - Disclosure - Loans Held for Investment - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LoansHeldforInvestmentNarrativeDetails</Role>
      <ShortName>Loans Held for Investment - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2423411 - Disclosure - Secured Financing Agreements - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SecuredFinancingAgreementsNarrativeDetails</Role>
      <ShortName>Secured Financing Agreements - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2424412 - Disclosure - Secured Financing Agreements - Schedule of Secured Financing Agreements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SecuredFinancingAgreementsScheduleofSecuredFinancingAgreementsDetails</Role>
      <ShortName>Secured Financing Agreements - Schedule of Secured Financing Agreements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2425413 - Disclosure - Secured Financing Agreements - Debt Maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SecuredFinancingAgreementsDebtMaturitiesDetails</Role>
      <ShortName>Secured Financing Agreements - Debt Maturities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2428414 - Disclosure - Fair Value of Financial Instruments - Recurring Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/FairValueofFinancialInstrumentsRecurringFairValueDetails</Role>
      <ShortName>Fair Value of Financial Instruments - Recurring Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2431415 - Disclosure - Shareholders' Equity - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/ShareholdersEquityNarrativeDetails</Role>
      <ShortName>Shareholders' Equity - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2432416 - Disclosure - Shareholders' Equity - Nonvested Share Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/ShareholdersEquityNonvestedShareActivityDetails</Role>
      <ShortName>Shareholders' Equity - Nonvested Share Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2433417 - Disclosure - Shareholders' Equity - Repurchases and Distributions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/ShareholdersEquityRepurchasesandDistributionsDetails</Role>
      <ShortName>Shareholders' Equity - Repurchases and Distributions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2435418 - Disclosure - Management Agreement with our Manager (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/ManagementAgreementwithourManagerDetails</Role>
      <ShortName>Management Agreement with our Manager (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/ManagementAgreementwithourManager</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2437419 - Disclosure - Related Person Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/RelatedPersonTransactionsDetails</Role>
      <ShortName>Related Person Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/RelatedPersonTransactions</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2439420 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/IncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/IncomeTaxes</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2442421 - Disclosure - Weighted Average Common Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/WeightedAverageCommonSharesDetails</Role>
      <ShortName>Weighted Average Common Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/WeightedAverageCommonSharesTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2444422 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/CommitmentsandContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sevnreit.com/role/CommitmentsandContingencies</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2446423 - Disclosure - Legal Proceedings - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/LegalProceedingsNarrativeDetails</Role>
      <ShortName>Legal Proceedings - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2448424 - Disclosure - SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Schedule of Mortgage Loans on Real Estate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SCHEDULEIVMORTGAGELOANSONREALESTATEScheduleofMortgageLoansonRealEstateDetails</Role>
      <ShortName>SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Schedule of Mortgage Loans on Real Estate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="sevn-20211231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2449425 - Disclosure - SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Reconciliation of Mortgage Loans on Real Estate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sevnreit.com/role/SCHEDULEIVMORTGAGELOANSONREALESTATEReconciliationofMortgageLoansonRealEstateDetails</Role>
      <ShortName>SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Reconciliation of Mortgage Loans on Real Estate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</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-K" original="sevn-20211231.htm">sevn-20211231.htm</File>
    <File>ex-81swopinion.htm</File>
    <File>exhibit1013citiguarantee.htm</File>
    <File>exhibit104-share_awardxagr.htm</File>
    <File>exhibit105-indemnification.htm</File>
    <File>exhibit211-listofsubsidiar.htm</File>
    <File>exhibit231deloitteconsent.htm</File>
    <File>exhibit232rsmconsent.htm</File>
    <File>exhibit41-sevenhills_.htm</File>
    <File>sevn-20211231.xsd</File>
    <File>sevn-20211231_cal.xml</File>
    <File>sevn-20211231_def.xml</File>
    <File>sevn-20211231_lab.xml</File>
    <File>sevn-20211231_pre.xml</File>
    <File>sevn_123121xexhibitx311.htm</File>
    <File>sevn_123121xexhibitx312.htm</File>
    <File>sevn_123121xexhibitx313.htm</File>
    <File>sevn_123121xexhibitx314.htm</File>
    <File>sevn_123121xexhibitx321.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="124">http://fasb.org/srt/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy items="382">http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy items="44">http://xbrl.sec.gov/dei/2021q4</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
