<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Version>2.4.0.6</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>236</ContextCount>
  <ElementCount>240</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>66</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>001 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>002 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>003 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>004 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>005 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>006 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/CondensedConsolidatedStatementsOfChangesInStockholdersEquity</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>007 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/CondensedConsolidatedStatementsOfChangesInStockholdersEquityParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>008 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>009 - Disclosure - BASIS OF PRESENTATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/BasisOfPresentation</Role>
      <ShortName>BASIS OF PRESENTATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>010 - Disclosure - SUMMARY OF ORGANIZATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/SummaryOfOrganization</Role>
      <ShortName>SUMMARY OF ORGANIZATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>011 - Disclosure - BUSINESS COMBINATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/BusinessCombination</Role>
      <ShortName>BUSINESS COMBINATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>012 - Disclosure - PREFERRED STOCK AND WARRANT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/PreferredStockAndWarrant</Role>
      <ShortName>PREFERRED STOCK AND WARRANT</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>013 - Disclosure - EARNINGS APPLICABLE TO COMMON STOCKHOLDERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/EarningsApplicableToCommonStockholders</Role>
      <ShortName>EARNINGS APPLICABLE TO COMMON STOCKHOLDERS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>014 - Disclosure - COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ComprehensiveIncome</Role>
      <ShortName>COMPREHENSIVE INCOME</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>015 - Disclosure - FAIR VALUE OF ASSETS AND LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/FairValueOfAssetsAndLiabilities</Role>
      <ShortName>FAIR VALUE OF ASSETS AND LIABILITIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>016 - Disclosure - LOANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/Loans</Role>
      <ShortName>LOANS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>017 - Disclosure - SECURITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/Securities</Role>
      <ShortName>SECURITIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>018 - Disclosure - ALLOWANCE FOR LOAN LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/AllowanceForLoanLosses</Role>
      <ShortName>ALLOWANCE FOR LOAN LOSSES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>019 - Disclosure - SUBSEQUENT EVENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/SubsequentEvents</Role>
      <ShortName>SUBSEQUENT EVENTS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>020 - Disclosure - RECLASSIFICATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/Reclassification</Role>
      <ShortName>RECLASSIFICATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>021 - Disclosure - BUSINESS COMBINATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/BusinessCombinationTables</Role>
      <ShortName>BUSINESS COMBINATION (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>022 - Disclosure - EARNINGS APPLICABLE TO COMMON STOCKHOLDERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/EarningsApplicableToCommonStockholdersTables</Role>
      <ShortName>EARNINGS APPLICABLE TO COMMON STOCKHOLDERS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>023 - Disclosure - COMPREHENSIVE INCOME (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ComprehensiveIncomeTables</Role>
      <ShortName>COMPREHENSIVE INCOME (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>024 - Disclosure - FAIR VALUE OF ASSETS AND LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/FairValueOfAssetsAndLiabilitiesTables</Role>
      <ShortName>FAIR VALUE OF ASSETS AND LIABILITIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>025 - Disclosure - LOANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/LoansTables</Role>
      <ShortName>LOANS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>026 - Disclosure - SECURITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/SecuritiesTables</Role>
      <ShortName>SECURITIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>027 - Disclosure - Summary of Organization - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/SummaryOfOrganizationAdditionalInformationDetail</Role>
      <ShortName>Summary of Organization - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>028 - Disclosure - Business Combination - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/BusinessCombinationAdditionalInformationDetail</Role>
      <ShortName>Business Combination - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>029 - Disclosure - Amounts of Acquired Identifiable Assets and Liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/AmountsOfAcquiredIdentifiableAssetsAndLiabilitiesDetail</Role>
      <ShortName>Amounts of Acquired Identifiable Assets and Liabilities (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>030 - Disclosure - Outstanding Principal Balance and Carrying Amount of Loans Included in Consolidated Balance Sheet (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/OutstandingPrincipalBalanceAndCarryingAmountOfLoansIncludedInConsolidatedBalanceSheetDetail</Role>
      <ShortName>Outstanding Principal Balance and Carrying Amount of Loans Included in Consolidated Balance Sheet (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>031 - Disclosure - Preferred Stock and Warrant - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/PreferredStockAndWarrantAdditionalInformationDetail</Role>
      <ShortName>Preferred Stock and Warrant - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>032 - Disclosure - Earnings Applicable to Common Stockholders (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/EarningsApplicableToCommonStockholdersDetail</Role>
      <ShortName>Earnings Applicable to Common Stockholders (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>033 - Disclosure - Earnings Applicable to Common Stockholders - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/EarningsApplicableToCommonStockholdersAdditionalInformationDetail</Role>
      <ShortName>Earnings Applicable to Common Stockholders - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>034 - Disclosure - Comprehensive Income Reported in Consolidated Statements of Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ComprehensiveIncomeReportedInConsolidatedStatementsOfIncomeDetail</Role>
      <ShortName>Comprehensive Income Reported in Consolidated Statements of Income (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>035 - Disclosure - Fair Value of Assets Measured on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/FairValueOfAssetsMeasuredOnRecurringBasisDetail</Role>
      <ShortName>Fair Value of Assets Measured on Recurring Basis (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>036 - Disclosure - Reconciliation of Activity for Assets Measured at Fair Value based on Significant Unobservable (Non-market) Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ReconciliationOfActivityForAssetsMeasuredAtFairValueBasedOnSignificantUnobservableNonMarketInformationDetail</Role>
      <ShortName>Reconciliation of Activity for Assets Measured at Fair Value based on Significant Unobservable (Non-market) Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>037 - Disclosure - Fair Value of Assets and Liabilities - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/FairValueOfAssetsAndLiabilitiesAdditionalInformationDetail</Role>
      <ShortName>Fair Value of Assets and Liabilities - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>038 - Disclosure - Fair Value of Assets Measured on Nonrecurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/FairValueOfAssetsMeasuredOnNonrecurringBasisDetail</Role>
      <ShortName>Fair Value of Assets Measured on Nonrecurring Basis (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>039 - Disclosure - Fair Values of off-Balance Sheet Financial Instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/FairValuesOfOffBalanceSheetFinancialInstrumentsDetail</Role>
      <ShortName>Fair Values of off-Balance Sheet Financial Instruments (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>040 - Disclosure - Loans - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/LoansAdditionalInformationDetail</Role>
      <ShortName>Loans - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>041 - Disclosure - Composition of Loan Portfolio (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/CompositionOfLoanPortfolioDetail</Role>
      <ShortName>Composition of Loan Portfolio (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>042 - Disclosure - Activity in Allowance for Loan Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ActivityInAllowanceForLoanLossesDetail</Role>
      <ShortName>Activity in Allowance for Loan Losses (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>043 - Disclosure - Allocation of Allowance for Loan Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/AllocationOfAllowanceForLoanLossesDetail</Role>
      <ShortName>Allocation of Allowance for Loan Losses (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>044 - Disclosure - Impaired Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/ImpairedLoansDetail</Role>
      <ShortName>Impaired Loans (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>045 - Disclosure - Summary of Interest Recognized and Cash-Basis Interest Earned on Impaired Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/SummaryOfInterestRecognizedAndCashBasisInterestEarnedOnImpairedLoansDetail</Role>
      <ShortName>Summary of Interest Recognized and Cash-Basis Interest Earned on Impaired Loans (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>046 - Disclosure - Loans and Allowance for Loan Losses, Broken Down by Portfolio Segment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/LoansAndAllowanceForLoanLossesBrokenDownByPortfolioSegmentDetail</Role>
      <ShortName>Loans and Allowance for Loan Losses, Broken Down by Portfolio Segment (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>047 - Disclosure - Additional Detail of Impaired Loans Broken Out According to Class (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/AdditionalDetailOfImpairedLoansBrokenOutAccordingToClassDetail</Role>
      <ShortName>Additional Detail of Impaired Loans Broken Out According to Class (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>048 - Disclosure - Additional Detail of Troubled Debt Restructurings (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/AdditionalDetailOfTroubledDebtRestructuringsDetail</Role>
      <ShortName>Additional Detail of Troubled Debt Restructurings (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>049 - Disclosure - Summary of Loans Classified as Past Due in Excess of Thirty Days or More and Loans Classified as Non-Accrual (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/SummaryOfLoansClassifiedAsPastDueInExcessOfThirtyDaysOrMoreAndLoansClassifiedAsNonAccrualDetail</Role>
      <ShortName>Summary of Loans Classified as Past Due in Excess of Thirty Days or More and Loans Classified as Non-Accrual (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>050 - Disclosure - Risk Category of Loans by Class of Loans (Excluding Mortgage Loans Held for Sale) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/RiskCategoryOfLoansByClassOfLoansExcludingMortgageLoansHeldForSaleDetail</Role>
      <ShortName>Risk Category of Loans by Class of Loans (Excluding Mortgage Loans Held for Sale) (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>051 - Disclosure - Summary of Amortized Cost and Estimated Fair Value of Available-For-Sale Securities and Held-To-Maturity Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.thefirstbank.com/role/SummaryOfAmortizedCostAndEstimatedFairValueOfAvailableForSaleSecuritiesAndHeldToMaturitySecuritiesDetail</Role>
      <ShortName>Summary of Amortized Cost and Estimated Fair Value of Available-For-Sale Securities and Held-To-Maturity Securities (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element fbms_AllowanceForCreditLossesPercentage had a mix of decimals attribute values: 2 3.</Log>
    <Log type="Info">Element fbms_PercentageOfLoanPortfolio had a mix of decimals attribute values: 2 3.</Log>
    <Log type="Info">Element us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_StockIssuedDuringPeriodSharesNewIssues had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">'Monetary' elements on report '028 - Disclosure - Business Combination - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '031 - Disclosure - Preferred Stock and Warrant - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 002 - Statement - CONSOLIDATED BALANCE SHEETS</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Sep. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2010'</Log>
    <Log type="Info">Process Flow-Through: 003 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 004 - Statement - CONSOLIDATED STATEMENTS OF INCOME</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2012'</Log>
    <Log type="Info">Process Flow-Through: 005 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</Log>
    <Log type="Info">Process Flow-Through: 007 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 008 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</Log>
  </Logs>
  <InputFiles>
    <File>fbms-20120930.xml</File>
    <File>fbms-20120930.xsd</File>
    <File>fbms-20120930_cal.xml</File>
    <File>fbms-20120930_def.xml</File>
    <File>fbms-20120930_lab.xml</File>
    <File>fbms-20120930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
