<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.5.0.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>277</ContextCount>
  <ElementCount>332</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>51</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Consolidated Statements Of Income And Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/ConsolidatedStatementsOfIncomeAndComprehensiveIncome</Role>
      <ShortName>Consolidated Statements Of Income And Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Consolidated Statements Of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/ConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>Consolidated Statements Of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003501 - Statement - Consolidated Statements Of Stockholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/ConsolidatedStatementsOfStockholdersEquityParenthetical</Role>
      <ShortName>Consolidated Statements Of Stockholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004000 - Statement - Consolidated Statements Of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements Of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Summary Of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary Of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/Securities</Role>
      <ShortName>Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/Loans</Role>
      <ShortName>Loans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivables</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/OtherComprehensiveIncome</Role>
      <ShortName>Other Comprehensive Income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/StockBasedCompensation</Role>
      <ShortName>Stock-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Guarantees</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/Guarantees</Role>
      <ShortName>Guarantees</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Fair Value Of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/FairValueOfFinancialInstruments</Role>
      <ShortName>Fair Value Of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Derivatives</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/Derivatives</Role>
      <ShortName>Derivatives</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Summary Of Significant Accounting Policies (Policy)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SummaryOfSignificantAccountingPoliciesPolicy</Role>
      <ShortName>Summary Of Significant Accounting Policies (Policy)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2302301 - Disclosure - Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SecuritiesTables</Role>
      <ShortName>Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/Securities</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Loans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/LoansTables</Role>
      <ShortName>Loans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/Loans</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesTables</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivables</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/EarningsPerShare</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/OtherComprehensiveIncomeTables</Role>
      <ShortName>Other Comprehensive Income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/OtherComprehensiveIncome</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/SegmentInformation</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Stock-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/StockBasedCompensationTables</Role>
      <ShortName>Stock-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/StockBasedCompensation</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Fair Value Of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/FairValueOfFinancialInstrumentsTables</Role>
      <ShortName>Fair Value Of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/FairValueOfFinancialInstruments</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Derivatives (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/DerivativesTables</Role>
      <ShortName>Derivatives (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/Derivatives</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - Summary Of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/SummaryOfSignificantAccountingPoliciesPolicy</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2402402 - Disclosure - Securities - Amortized Cost And Approximate Fair Value Of Securities Available For Sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SecuritiesAmortizedCostAndApproximateFairValueOfSecuritiesAvailableForSaleDetails</Role>
      <ShortName>Securities - Amortized Cost And Approximate Fair Value Of Securities Available For Sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2402403 - Disclosure - Securities - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SecuritiesAdditionalInformationDetails</Role>
      <ShortName>Securities - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2402404 - Disclosure - Securities - Amortized Cost And Fair Value Of Securities By Contractual Maturity Of Available-For-Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SecuritiesAmortizedCostAndFairValueOfSecuritiesByContractualMaturityOfAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Securities - Amortized Cost And Fair Value Of Securities By Contractual Maturity Of Available-For-Sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2402405 - Disclosure - Securities - Temporarily Impaired Gross Unrealized Losses And Fair Value Of Available-For-Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SecuritiesTemporarilyImpairedGrossUnrealizedLossesAndFairValueOfAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Securities - Temporarily Impaired Gross Unrealized Losses And Fair Value Of Available-For-Sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2402406 - Disclosure - Securities - Amortized Cost And Approximate Fair Value Of Securities Held-To-Maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SecuritiesAmortizedCostAndApproximateFairValueOfSecuritiesHeldToMaturityDetails</Role>
      <ShortName>Securities - Amortized Cost And Approximate Fair Value Of Securities Held-To-Maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2402407 - Disclosure - Securities - Amortized Cost And Fair Value Of Securities By Contractual Maturity Of Held-To-Maturity Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SecuritiesAmortizedCostAndFairValueOfSecuritiesByContractualMaturityOfHeldToMaturitySecuritiesDetails</Role>
      <ShortName>Securities - Amortized Cost And Fair Value Of Securities By Contractual Maturity Of Held-To-Maturity Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Loans - Composition Of Net Loans Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/LoansCompositionOfNetLoansReceivableDetails</Role>
      <ShortName>Loans - Composition Of Net Loans Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Changes In The Allowance For Loan Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesChangesInAllowanceForLoanLossesDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Changes In The Allowance For Loan Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Allowances Of Loan Losses And Loans Receivable By Class Disaggregated (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesAllowancesOfLoanLossesAndLoansReceivableByClassDisaggregatedDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Allowances Of Loan Losses And Loans Receivable By Class Disaggregated (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Age Analysis Of Loans Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesAgeAnalysisOfLoansReceivableDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Age Analysis Of Loans Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Loans Which The Accrual Of Interest Has Been Discontinued (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesLoansWhichAccrualOfInterestHasBeenDiscontinuedDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Loans Which The Accrual Of Interest Has Been Discontinued (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2404406 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Credit Risk Profile By Creditworthiness (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesCreditRiskProfileByCreditworthinessDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Credit Risk Profile By Creditworthiness (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2404407 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesImpairedLoansDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Impaired Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2404408 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Troubled Debt Restructured On Recorded Investment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesTroubledDebtRestructuredOnRecordedInvestmentDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Troubled Debt Restructured On Recorded Investment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2404409 - Disclosure - Allowance For Loan Losses And Credit Quality Of Financing Receivables - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/AllowanceForLoanLossesAndCreditQualityOfFinancingReceivablesAdditionalInformationDetails</Role>
      <ShortName>Allowance For Loan Losses And Credit Quality Of Financing Receivables - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/EarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/EarningsPerShareTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/OtherComprehensiveIncomeDetails</Role>
      <ShortName>Other Comprehensive Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/OtherComprehensiveIncomeTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/SegmentInformationDetails</Role>
      <ShortName>Segment Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/SegmentInformationTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Stock-Based Compensation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/StockBasedCompensationAdditionalInformationDetails</Role>
      <ShortName>Stock-Based Compensation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Stock-Based Compensation - Summary Of Information Regarding Stock Option Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/StockBasedCompensationSummaryOfInformationRegardingStockOptionPlansDetails</Role>
      <ShortName>Stock-Based Compensation - Summary Of Information Regarding Stock Option Plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2408404 - Disclosure - Stock-Based Compensation - Summary Of Stock Option Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/StockBasedCompensationSummaryOfStockOptionAssumptionsDetails</Role>
      <ShortName>Stock-Based Compensation - Summary Of Stock Option Assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2408405 - Disclosure - Stock-Based Compensation - Summary Of Information Regarding Restricted Stock Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/StockBasedCompensationSummaryOfInformationRegardingRestrictedStockActivityDetails</Role>
      <ShortName>Stock-Based Compensation - Summary Of Information Regarding Restricted Stock Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2409401 - Disclosure - Guarantees (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/GuaranteesDetails</Role>
      <ShortName>Guarantees (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.sussexbank.com/role/Guarantees</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Fair Value Of Financial Instruments - Summary Of Financial Assets Measured On A Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/FairValueOfFinancialInstrumentsSummaryOfFinancialAssetsMeasuredOnRecurringBasisDetails</Role>
      <ShortName>Fair Value Of Financial Instruments - Summary Of Financial Assets Measured On A Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Fair Value Of Financial Instruments - Summary Of Financial Assets Measured On A Nonrecurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/FairValueOfFinancialInstrumentsSummaryOfFinancialAssetsMeasuredOnNonrecurringBasisDetails</Role>
      <ShortName>Fair Value Of Financial Instruments - Summary Of Financial Assets Measured On A Nonrecurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2410404 - Disclosure - Fair Value Of Financial Instruments - Qualitative Information About Level 3 Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/FairValueOfFinancialInstrumentsQualitativeInformationAboutLevel3FairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Of Financial Instruments - Qualitative Information About Level 3 Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - Fair Value Of Financial Instruments - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/FairValueOfFinancialInstrumentsAdditionalInformationDetails</Role>
      <ShortName>Fair Value Of Financial Instruments - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2410406 - Disclosure - Fair Value Of Financial Instruments - Estimated Fair Values Of Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/FairValueOfFinancialInstrumentsEstimatedFairValuesOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Of Financial Instruments - Estimated Fair Values Of Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Derivatives - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/DerivativesAdditionalInformationDetails</Role>
      <ShortName>Derivatives - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Derivatives - Schedule Of Fair Value of Derivatives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/DerivativesScheduleOfFairValueOfDerivativesDetails</Role>
      <ShortName>Derivatives - Schedule Of Fair Value of Derivatives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="sbbx-20160930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - Derivatives - Schedule Of Derivative Financial Instruments Designated As Cash Flow Hedges (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sussexbank.com/role/DerivativesScheduleOfDerivativeFinancialInstrumentsDesignatedAsCashFlowHedgesDetails</Role>
      <ShortName>Derivatives - Schedule Of Derivative Financial Instruments Designated As Cash Flow Hedges (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>sbbx-20160930.xml</File>
    <File>sbbx-20160930.xsd</File>
    <File>sbbx-20160930_cal.xml</File>
    <File>sbbx-20160930_def.xml</File>
    <File>sbbx-20160930_lab.xml</File>
    <File>sbbx-20160930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies/>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
