<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.8.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>357</ContextCount>
  <ElementCount>548</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>81</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>11</UnitCount>
  <MyReports>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000100 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>010000 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ConsolidatedStatementsOfFinancialCondition</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>010100 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ConsolidatedStatementsOfFinancialConditionParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>020000 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ConsolidatedStatementsOfOperations</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>030000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>030100 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ConsolidatedStatementsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>040000 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ConsolidatedStatementsOfChangesInStockholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>050000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>060100 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>060200 - Disclosure - Correction of an Immaterial Prior Year Error</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/CorrectionOfImmaterialPriorYearError</Role>
      <ShortName>Correction of an Immaterial Prior Year Error</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>060300 - Disclosure - Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/Securities</Role>
      <ShortName>Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>060400 - Disclosure - Loans Receivable and Allowance for Loan Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLosses</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>060500 - Disclosure - Premises and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/PremisesAndEquipment</Role>
      <ShortName>Premises and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>060600 - Disclosure - Goodwill and Other Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/GoodwillAndOtherIntangibleAssets</Role>
      <ShortName>Goodwill and Other Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>060700 - Disclosure - Deposits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/Deposits</Role>
      <ShortName>Deposits</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>060800 - Disclosure - Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/Borrowings</Role>
      <ShortName>Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>060900 - Disclosure - Subordinated Debentures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/SubordinatedDebentures</Role>
      <ShortName>Subordinated Debentures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>061000 - Disclosure - Employee Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/EmployeeBenefitPlans</Role>
      <ShortName>Employee Benefit Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>061100 - Disclosure - Regulatory Matters</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/RegulatoryMatters</Role>
      <ShortName>Regulatory Matters</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>061200 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>061300 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>061400 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/StockbasedCompensation</Role>
      <ShortName>Stock-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>061500 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>061600 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>061700 - Disclosure - Fair Value of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/FairValueOfFinancialInstruments</Role>
      <ShortName>Fair Value of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>061800 - Disclosure - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/RelatedPartyTransactions</Role>
      <ShortName>Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>061900 - Disclosure - Parent Company Financial Statements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ParentCompanyFinancialStatements</Role>
      <ShortName>Parent Company Financial Statements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>070100 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/SummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://severnbank.com/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>080300 - Disclosure - Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/SecuritiesTables</Role>
      <ShortName>Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/Securities</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>080400 - Disclosure - Loans Receivable and Allowance for Loan Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLossesTables</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLosses</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>080500 - Disclosure - Premises and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/PremisesAndEquipmentTables</Role>
      <ShortName>Premises and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/PremisesAndEquipment</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>080600 - Disclosure - Goodwill and Other Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/GoodwillAndOtherIntangibleAssetsTables</Role>
      <ShortName>Goodwill and Other Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/GoodwillAndOtherIntangibleAssets</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>080700 - Disclosure - Deposits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/DepositsTables</Role>
      <ShortName>Deposits (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/Deposits</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>080800 - Disclosure - Borrowings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/BorrowingsTables</Role>
      <ShortName>Borrowings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/Borrowings</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>081100 - Disclosure - Regulatory Matters (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/RegulatoryMattersTables</Role>
      <ShortName>Regulatory Matters (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/RegulatoryMatters</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>081300 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/EarningsPerShare</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>081400 - Disclosure - Stock-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/StockbasedCompensationTables</Role>
      <ShortName>Stock-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/StockbasedCompensation</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>081500 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/IncomeTaxes</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>081600 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/CommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/CommitmentsAndContingencies</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>081700 - Disclosure - Fair Value of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/FairValueOfFinancialInstrumentsTables</Role>
      <ShortName>Fair Value of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/FairValueOfFinancialInstruments</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>081800 - Disclosure - Related Party Transactions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/RelatedPartyTransactionsTables</Role>
      <ShortName>Related Party Transactions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/RelatedPartyTransactions</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>081900 - Disclosure - Parent Company Financial Statements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ParentCompanyFinancialStatementsTables</Role>
      <ShortName>Parent Company Financial Statements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://severnbank.com/role/ParentCompanyFinancialStatements</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>090100 - Disclosure - Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/SummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/SummaryOfSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>090200 - Disclosure - Correction of an Immaterial Prior Year Error (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/CorrectionOfImmaterialPriorYearErrorDetails</Role>
      <ShortName>Correction of an Immaterial Prior Year Error (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/CorrectionOfImmaterialPriorYearError</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>090300 - Disclosure - Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/SecuritiesDetails</Role>
      <ShortName>Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/SecuritiesTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>090400 - Disclosure - Loans Receivable and Allowance for Loan Losses, Summary of Loans Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLossesSummaryOfLoansReceivableDetails</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses, Summary of Loans Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>090402 - Disclosure - Loans Receivable and Allowance for Loan Losses, Changes in Allowance For Loan Losses and Recorded Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLossesChangesInAllowanceForLoanLossesAndRecordedInvestmentsDetails</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses, Changes in Allowance For Loan Losses and Recorded Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>090406 - Disclosure - Loans Receivable and Allowance for Loan Losses, Credit Quality Breakdown of Loan Portfolio by Class (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLossesCreditQualityBreakdownOfLoanPortfolioByClassDetails</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses, Credit Quality Breakdown of Loan Portfolio by Class (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>090408 - Disclosure - Loans Receivable and Allowance for Loan Losses, Classes of Loan Portfolio by Aging Categories of Performing and Nonaccrual Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLossesClassesOfLoanPortfolioByAgingCategoriesOfPerformingAndNonaccrualLoansDetails</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses, Classes of Loan Portfolio by Aging Categories of Performing and Nonaccrual Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>090414 - Disclosure - Loans Receivable and Allowance for Loan Losses, Summary of Impaired loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLossesSummaryOfImpairedLoansDetails</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses, Summary of Impaired loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>090416 - Disclosure - Loans Receivable and Allowance for Loan Losses, Loans modified as TDRs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/LoansReceivableAndAllowanceForLoanLossesLoansModifiedAsTdrsDetails</Role>
      <ShortName>Loans Receivable and Allowance for Loan Losses, Loans modified as TDRs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>090500 - Disclosure - Premises and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/PremisesAndEquipmentDetails</Role>
      <ShortName>Premises and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/PremisesAndEquipmentTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>090600 - Disclosure - Goodwill and Other Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/GoodwillAndOtherIntangibleAssetsDetails</Role>
      <ShortName>Goodwill and Other Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>090700 - Disclosure - Deposits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/DepositsDetails</Role>
      <ShortName>Deposits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/DepositsTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>090800 - Disclosure - Borrowings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/BorrowingsDetails</Role>
      <ShortName>Borrowings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/BorrowingsTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>090900 - Disclosure - Subordinated Debentures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/SubordinatedDebenturesDetails</Role>
      <ShortName>Subordinated Debentures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/SubordinatedDebentures</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>091000 - Disclosure - Employee Benefit Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/EmployeeBenefitPlansDetails</Role>
      <ShortName>Employee Benefit Plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/EmployeeBenefitPlans</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>091100 - Disclosure - Regulatory Matters (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/RegulatoryMattersDetails</Role>
      <ShortName>Regulatory Matters (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/RegulatoryMattersTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>091200 - Disclosure - Stockholders' Equity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/StockholdersEquityDetails</Role>
      <ShortName>Stockholders' Equity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/StockholdersEquity</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>091300 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/EarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/EarningsPerShareTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>091400 - Disclosure - Stock-Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/StockbasedCompensationDetails</Role>
      <ShortName>Stock-Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/StockbasedCompensationTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>091500 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/IncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/IncomeTaxesTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>091600 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/CommitmentsAndContingenciesTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>091700 - Disclosure - Fair Value of Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/FairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value of Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/FairValueOfFinancialInstrumentsTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>091702 - Disclosure - Fair Value of Financial Instruments, Assets, Quantitative Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/FairValueOfFinancialInstrumentsAssetsQuantitativeInformationDetails</Role>
      <ShortName>Fair Value of Financial Instruments, Assets, Quantitative Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>091704 - Disclosure - Fair Value of Financial Instruments, Assets, Balance Sheet Grouping (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/FairValueOfFinancialInstrumentsAssetsBalanceSheetGroupingDetails</Role>
      <ShortName>Fair Value of Financial Instruments, Assets, Balance Sheet Grouping (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>091800 - Disclosure - Related Party Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/RelatedPartyTransactionsDetails</Role>
      <ShortName>Related Party Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/RelatedPartyTransactionsTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="svbi-20171231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>091900 - Disclosure - Parent Company Financial Statements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://severnbank.com/role/ParentCompanyFinancialStatementsDetails</Role>
      <ShortName>Parent Company Financial Statements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://severnbank.com/role/ParentCompanyFinancialStatementsTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>svbi-20171231.xml</File>
    <File>svbi-20171231.xsd</File>
    <File>svbi-20171231_cal.xml</File>
    <File>svbi-20171231_def.xml</File>
    <File>svbi-20171231_lab.xml</File>
    <File>svbi-20171231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/us-gaap/2017-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2014-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
