<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.21.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>433</ContextCount>
  <ElementCount>378</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>55</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>00010 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/Documentandentityinformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>00020 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>00030 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>00040 - Statement - CONSOLIDATED STATEMENTS OF INCOME (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>00050 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>00060 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY  (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ConsolidatedStatementsOfShareholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY  (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>00070 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>00080 - Disclosure - Nature of Business and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/NatureOfBusinessAndBasisOfPresentation</Role>
      <ShortName>Nature of Business and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>00090 - Disclosure - Investment Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/InvestmentSecurities</Role>
      <ShortName>Investment Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>00100 - Disclosure - Mortgage Loans Held for Sale</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/MortgageLoansHeldForSale</Role>
      <ShortName>Mortgage Loans Held for Sale</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>00110 - Disclosure - Loans and Allowance for Loan Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLosses</Role>
      <ShortName>Loans and Allowance for Loan Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>00120 - Disclosure - Troubled Debt Restructurings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/TroubledDebtRestructurings</Role>
      <ShortName>Troubled Debt Restructurings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>00130 - Disclosure - Derivative Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/DerivativeFinancialInstruments</Role>
      <ShortName>Derivative Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>00140 - Disclosure - Fair Value Accounting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/FairValueAccounting</Role>
      <ShortName>Fair Value Accounting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>00150 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>00160 - Disclosure - Earnings Per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/EarningsPerCommonShare</Role>
      <ShortName>Earnings Per Common Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>00170 - Disclosure - Reportable Segments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ReportableSegments</Role>
      <ShortName>Reportable Segments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>00180 - Disclosure - Nature of Business and Basis of Presentation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/NatureOfBusinessAndBasisOfPresentationPolicies</Role>
      <ShortName>Nature of Business and Basis of Presentation (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://southernfirst.com/role/FairValueAccounting</ParentRole>
      <Position>18</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>00190 - Disclosure - Investment Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/InvestmentSecuritiesTables</Role>
      <ShortName>Investment Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/InvestmentSecurities</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>00200 - Disclosure - Loans and Allowance for Loan Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</Role>
      <ShortName>Loans and Allowance for Loan Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansAndAllowanceForLoanLosses</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>00210 - Disclosure - Troubled Debt Restructurings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/TroubledDebtRestructuringsTables</Role>
      <ShortName>Troubled Debt Restructurings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/TroubledDebtRestructurings</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>00220 - Disclosure - Derivative Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/DerivativeFinancialInstrumentsTables</Role>
      <ShortName>Derivative Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/DerivativeFinancialInstruments</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>00230 - Disclosure - Fair Value Accounting (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/FairValueAccountingTables</Role>
      <ShortName>Fair Value Accounting (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/FairValueAccounting</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>00240 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/Leases</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>00250 - Disclosure - Earnings Per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/Earningspercommonsharetables</Role>
      <ShortName>Earnings Per Common Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/EarningsPerCommonShare</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>00260 - Disclosure - Reportable Segments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ReportableSegmentsTables</Role>
      <ShortName>Reportable Segments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://southernfirst.com/role/ReportableSegments</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>00270 - Disclosure - Nature of Business and Basis of Presentation (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/NatureOfBusinessAndBasisOfPresentationNarrativeDetails</Role>
      <ShortName>Nature of Business and Basis of Presentation (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/NatureOfBusinessAndBasisOfPresentationPolicies</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>00280 - Disclosure - Investment Securities (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/InvestmentSecuritiesNarrativeDetails</Role>
      <ShortName>Investment Securities (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>00290 - Disclosure - Investment Securities (Schedule of Amortized Costs and Fair Value of Investment Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/InvestmentSecuritiesScheduleOfAmortizedCostsAndFairValueOfInvestmentSecuritiesDetails</Role>
      <ShortName>Investment Securities (Schedule of Amortized Costs and Fair Value of Investment Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>00300 - Disclosure - Investment Securities (Schedule of Fair Values Investment Securities Available for Contractual Maturities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/InvestmentSecuritiesScheduleOfFairValuesInvestmentSecuritiesAvailableForContractualMaturitiesDetails</Role>
      <ShortName>Investment Securities (Schedule of Fair Values Investment Securities Available for Contractual Maturities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>00310 - Disclosure - Investment Securities (Schedule of Gross Unrealized Losses on Investment Securities and Fair Market Value) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/InvestmentSecuritiesScheduleOfGrossUnrealizedLossesOnInvestmentSecuritiesAndFairMarketValueDetails</Role>
      <ShortName>Investment Securities (Schedule of Gross Unrealized Losses on Investment Securities and Fair Market Value) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>00320 - Disclosure - Investment Securities (Schedule of Other Investments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/InvestmentSecuritiesScheduleOfOtherInvestmentsDetails</Role>
      <ShortName>Investment Securities (Schedule of Other Investments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>00330 - Disclosure - Mortgage Loans Held for Sale (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/MortgageLoansHeldForSaleNarrativeDetails</Role>
      <ShortName>Mortgage Loans Held for Sale (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/MortgageLoansHeldForSale</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>00340 - Disclosure - Loans and Allowance for Loan Losses (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesNarrativeDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>00350 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Composition of Loan Portfolio) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfCompositionOfLoanPortfolioDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Composition of Loan Portfolio) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>00360 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Loan Maturity Distribution by Type and Related Interest Rate) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfLoanMaturityDistributionByTypeAndRelatedInterestRateDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Loan Maturity Distribution by Type and Related Interest Rate) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>00370 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Outstanding Commercial and Consumer Loans as Non-Accruals by Class) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfOutstandingCommercialAndConsumerLoansAsNon-accrualsByClassDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Outstanding Commercial and Consumer Loans as Non-Accruals by Class) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>00380 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Breakdown of Outstanding Loans by Risk Category) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfBreakdownOfOutstandingLoansByRiskCategoryDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Breakdown of Outstanding Loans by Risk Category) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>00390 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Aging of Past Due Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfAgingOfPastDueLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Aging of Past Due Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>00400 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Outstanding Consumer Loans by Risk Category) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfOutstandingConsumerLoansByRiskCategoryDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Outstanding Consumer Loans by Risk Category) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>00410 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Nonperforming Assets, Including Nonaccruing TDRs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfNonperformingAssetsIncludingNonaccruingTdrsDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Nonperforming Assets, Including Nonaccruing TDRs) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>00420 - Disclosure - Loans and Allowance for Loan Losses (Schedule of Key Information for Impaired Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesScheduleOfKeyInformationForImpairedLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Schedule of Key Information for Impaired Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>00430 - Disclosure - Loans and Allowance for Loan Losses (Average Recorded Investment and Interest Income Recognized on Impaired Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesAverageRecordedInvestmentAndInterestIncomeRecognizedOnImpairedLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Average Recorded Investment and Interest Income Recognized on Impaired Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>00440 - Disclosure - Loans and Allowance for Loan Losses (Allowance for Loan Losses by Commercial and Consumer Portfolio Segments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesAllowanceForLoanLossesByCommercialAndConsumerPortfolioSegmentsDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Allowance for Loan Losses by Commercial and Consumer Portfolio Segments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>00450 - Disclosure - Loans and Allowance for Loan Losses (Allowance for Loan Losses and Recorded Investment in Loans by Impairment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LoansAndAllowanceForLoanLossesAllowanceForLoanLossesAndRecordedInvestmentInLoansByImpairmentDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses (Allowance for Loan Losses and Recorded Investment in Loans by Impairment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LoansandAllowanceforLoanLossesTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>00460 - Disclosure - Troubled Debt Restructurings (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/TroubledDebtRestructuringsNarrativeDetails</Role>
      <ShortName>Troubled Debt Restructurings (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/TroubledDebtRestructuringsTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>00470 - Disclosure - Troubled Debt Restructurings (Summary of Concession at the Time Of Modification) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/TroubledDebtRestructuringsSummaryOfConcessionAtTimeOfModificationDetails</Role>
      <ShortName>Troubled Debt Restructurings (Summary of Concession at the Time Of Modification) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/TroubledDebtRestructuringsTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>00480 - Disclosure - Derivative Financial Instruments (Schedule of Outstanding Financial Derivative Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/DerivativeFinancialInstrumentsScheduleOfOutstandingFinancialDerivativeInstrumentsDetails</Role>
      <ShortName>Derivative Financial Instruments (Schedule of Outstanding Financial Derivative Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/DerivativeFinancialInstrumentsTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>00490 - Disclosure - Fair Value Accounting (Schedule of Assets And Liabilities Measured at Fair Value on Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/FairValueAccountingScheduleOfAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails</Role>
      <ShortName>Fair Value Accounting (Schedule of Assets And Liabilities Measured at Fair Value on Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/FairValueAccountingTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>00500 - Disclosure - Fair Value Accounting (Schedule of Assets And Liabilities Measured at Fair Value on Nonrecurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/FairValueAccountingScheduleOfAssetsAndLiabilitiesMeasuredAtFairValueOnNonrecurringBasisDetails</Role>
      <ShortName>Fair Value Accounting (Schedule of Assets And Liabilities Measured at Fair Value on Nonrecurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/FairValueAccountingTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>00510 - Disclosure - Fair Value Accounting (Schedule of Estimated Fair Values of the Company's Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/FairValueAccountingScheduleOfEstimatedFairValuesOfCompanysFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Accounting (Schedule of Estimated Fair Values of the Company's Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/FairValueAccountingTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>00520 - Disclosure - Leases (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LeasesNarrativeDetails</Role>
      <ShortName>Leases (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LeasesTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>00530 - Disclosure - Leases (Maturities of lease liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/LeasesMaturitiesOfLeaseLiabilitiesDetails</Role>
      <ShortName>Leases (Maturities of lease liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/LeasesTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>00540 - Disclosure - Earnings Per Common Share (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/EarningsPerCommonShareNarrativeDetails</Role>
      <ShortName>Earnings Per Common Share (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/Earningspercommonsharetables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>00550 - Disclosure - Earnings Per Common Share (Schedule of Earnings Per Share Calculation) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/EarningsPerCommonShareScheduleOfEarningsPerShareCalculationDetails</Role>
      <ShortName>Earnings Per Common Share (Schedule of Earnings Per Share Calculation) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/Earningspercommonsharetables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>00560 - Disclosure - Reportable Segments (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ReportableSegmentsNarrativeDetails</Role>
      <ShortName>Reportable Segments (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/ReportableSegmentsTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="sfb3937681-10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>00570 - Disclosure - Reportable Segments (Schedule of financial information for each reportable segment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://southernfirst.com/role/ReportableSegmentsScheduleOfFinancialInformationForEachReportableSegmentDetails</Role>
      <ShortName>Reportable Segments (Schedule of financial information for each reportable segment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://southernfirst.com/role/ReportableSegmentsTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="sfb3937681-10q.htm">sfb3937681-10q.htm</File>
    <File>sfb3937681-ex311.htm</File>
    <File>sfb3937681-ex312.htm</File>
    <File>sfb3937681-ex32.htm</File>
    <File>sfst-20210630.xsd</File>
    <File>sfst-20210630_cal.xml</File>
    <File>sfst-20210630_def.xml</File>
    <File>sfst-20210630_lab.xml</File>
    <File>sfst-20210630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>sfst-logo.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2021</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
