<?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>484</ContextCount>
  <ElementCount>633</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>97</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0010 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/BalanceSheet</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>0015 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/BalanceSheetParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>0020 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/StatementOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>0030 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/StatementOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>0040 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/StatementOfStockholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>0045 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/StatementOfStockholdersEquityParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>0050 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/CashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>1010 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>1020 - Disclosure - PREFERRED STOCK AND STOCK REPURCHASE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosurePreferredStockAndStockRepurchase</Role>
      <ShortName>PREFERRED STOCK AND STOCK REPURCHASE</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>1030 - Disclosure - RESTRICTION ON CASH AND DUE FROM BANKS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRestrictionOnCashAndDueFromBanks</Role>
      <ShortName>RESTRICTION ON CASH AND DUE FROM BANKS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>1040 - Disclosure - SECURITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSecurities</Role>
      <ShortName>SECURITIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>1050 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLosses</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>1060 - Disclosure - OTHER REAL ESTATE OWNED</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureOtherRealEstateOwned</Role>
      <ShortName>OTHER REAL ESTATE OWNED</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>1070 - Disclosure - FAIR VALUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValue</Role>
      <ShortName>FAIR VALUE</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>1080 - Disclosure - PREMISES AND EQUIPMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosurePremisesAndEquipment</Role>
      <ShortName>PREMISES AND EQUIPMENT</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>1090 - Disclosure - GOODWILL AND INTANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureGoodwillAndIntangibleAssets</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>1100 - Disclosure - DEPOSITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureDeposits</Role>
      <ShortName>DEPOSITS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>1110 - Disclosure - OTHER BORROWINGS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureOtherBorrowings</Role>
      <ShortName>OTHER BORROWINGS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>1120 - Disclosure - FEDERAL HOME LOAN BANK ADVANCES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFederalHomeLoanBankAdvances</Role>
      <ShortName>FEDERAL HOME LOAN BANK ADVANCES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>1130 - Disclosure - SUBORDINATED DEBENTURES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSubordinatedDebentures</Role>
      <ShortName>SUBORDINATED DEBENTURES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>1140 - Disclosure - MORTGAGE BANKING AND LOAN SERVICING</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureMortgageBankingAndLoanServicing</Role>
      <ShortName>MORTGAGE BANKING AND LOAN SERVICING</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>1150 - Disclosure - INCOME TAX</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureIncomeTax</Role>
      <ShortName>INCOME TAX</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>1160 - Disclosure - COMMITMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureCommitments</Role>
      <ShortName>COMMITMENTS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>1170 - Disclosure - DIVIDENDS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureDividends</Role>
      <ShortName>DIVIDENDS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>1180 - Disclosure - DIVIDEND REINVESTMENT PLAN</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureDividendReinvestmentPlan</Role>
      <ShortName>DIVIDEND REINVESTMENT PLAN</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>1190 - Disclosure - REGULATORY MATTERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRegulatoryMatters</Role>
      <ShortName>REGULATORY MATTERS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>1200 - Disclosure - EMPLOYEE BENEFIT PLANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureEmployeeBenefitPlans</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>1210 - Disclosure - RELATED PARTY TRANSACTIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRelatedPartyTransactions</Role>
      <ShortName>RELATED PARTY TRANSACTIONS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>1220 - Disclosure - STOCK-BASED COMPENSATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureStockBasedCompensation</Role>
      <ShortName>STOCK-BASED COMPENSATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>1230 - Disclosure - EARNINGS PER COMMON SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureEarningsPerCommonShare</Role>
      <ShortName>EARNINGS PER COMMON SHARE</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>1240 - Disclosure - QUARTERLY FINANCIAL DATA (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureQuarterlyFinancialData</Role>
      <ShortName>QUARTERLY FINANCIAL DATA (UNAUDITED)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>1250 - Disclosure - PARENT ONLY CONDENSED FINANCIAL STATEMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureParentOnlyCondensedFinancialStatements</Role>
      <ShortName>PARENT ONLY CONDENSED FINANCIAL STATEMENTS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>1260 - Disclosure - ACQUISITIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureAcquisitions</Role>
      <ShortName>ACQUISITIONS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>1270 - Disclosure - SUBSEQUENT EVENT - BRANCH CLOSURES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSubsequentEvent</Role>
      <ShortName>SUBSEQUENT EVENT - BRANCH CLOSURES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2010 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>3040 - Disclosure - SECURITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSecuritiesTables</Role>
      <ShortName>SECURITIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>3050 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesTables</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>3060 - Disclosure - OTHER REAL ESTATE OWNED (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureOtherRealEstateOwnedTables</Role>
      <ShortName>OTHER REAL ESTATE OWNED (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>3070 - Disclosure - FAIR VALUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValueTables</Role>
      <ShortName>FAIR VALUE (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>3080 - Disclosure - PREMISES AND EQUIPMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosurePremisesAndEquipmentTables</Role>
      <ShortName>PREMISES AND EQUIPMENT (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>3090 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureGoodwillAndIntangibleAssetsTables</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>3100 - Disclosure - DEPOSITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureDepositsTables</Role>
      <ShortName>DEPOSITS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>3110 - Disclosure - OTHER BORROWINGS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureOtherBorrowingsTables</Role>
      <ShortName>OTHER BORROWINGS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>3120 - Disclosure - FEDERAL HOME LOAN BANK ADVANCES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFederalHomeLoanBankAdvancesTables</Role>
      <ShortName>FEDERAL HOME LOAN BANK ADVANCES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>3130 - Disclosure - SUBORDINATED DEBENTURES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSubordinatedDebenturesTables</Role>
      <ShortName>SUBORDINATED DEBENTURES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>3140 - Disclosure - MORTGAGE BANKING AND LOAN SERVICING (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureMortgageBankingAndLoanServicingTables</Role>
      <ShortName>MORTGAGE BANKING AND LOAN SERVICING (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>3150 - Disclosure - INCOME TAX (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureIncomeTaxTables</Role>
      <ShortName>INCOME TAX (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>3160 - Disclosure - COMMITMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureCommitmentsTables</Role>
      <ShortName>COMMITMENTS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>3190 - Disclosure - REGULATORY MATTERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRegulatoryMattersTables</Role>
      <ShortName>REGULATORY MATTERS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>3210 - Disclosure - RELATED PARTY TRANSACTIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRelatedPartyTransactionsTables</Role>
      <ShortName>RELATED PARTY TRANSACTIONS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>3220 - Disclosure - STOCK-BASED COMPENSATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureStockBasedCompensationTables</Role>
      <ShortName>STOCK-BASED COMPENSATION (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>3230 - Disclosure - EARNINGS PER COMMON SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureEarningsPerCommonShareTables</Role>
      <ShortName>EARNINGS PER COMMON SHARE (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>3240 - Disclosure - QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureQuarterlyFinancialDataTables</Role>
      <ShortName>QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>3250 - Disclosure - PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureParentOnlyCondensedFinancialStatementsTables</Role>
      <ShortName>PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>4010 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>4011 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails2</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>4012 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails3</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>4020 - Disclosure - PREFERRED STOCK AND STOCK REPURCHASE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosurePreferredStockAndStockRepurchaseDetails</Role>
      <ShortName>PREFERRED STOCK AND STOCK REPURCHASE (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>4030 - Disclosure - RESTRICTION ON CASH AND DUE FROM BANKS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRestrictionOnCashAndDueFromBanksDetails</Role>
      <ShortName>RESTRICTION ON CASH AND DUE FROM BANKS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>4040 - Disclosure - SECURITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSecuritiesDetails</Role>
      <ShortName>SECURITIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>4050 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>4051 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesDetails2</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>4052 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesDetails3</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 3)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>4053 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 4)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesDetails4</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 4)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>4054 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 5)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesDetails5</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 5)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>4055 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 6)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesDetails6</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 6)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>4056 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 7)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureLoansAndAllowanceForLoanLossesDetails7</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 7)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>4060 - Disclosure - OTHER REAL ESTATE OWNED (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureOtherRealEstateOwnedDetails</Role>
      <ShortName>OTHER REAL ESTATE OWNED (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>4070 - Disclosure - FAIR VALUE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValueDetails</Role>
      <ShortName>FAIR VALUE (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>4071 - Disclosure - FAIR VALUE (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValueDetails2</Role>
      <ShortName>FAIR VALUE (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>4072 - Disclosure - FAIR VALUE (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValueDetails3</Role>
      <ShortName>FAIR VALUE (Details 3)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>4073 - Disclosure - FAIR VALUE (Details 4)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValueDetails4</Role>
      <ShortName>FAIR VALUE (Details 4)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>4074 - Disclosure - FAIR VALUE (Details 5)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValueDetails5</Role>
      <ShortName>FAIR VALUE (Details 5)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>4075 - Disclosure - FAIR VALUE (Details 6)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFairValueDetails6</Role>
      <ShortName>FAIR VALUE (Details 6)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>4080 - Disclosure - PREMISES AND EQUIPMENT (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosurePremisesAndEquipmentDetails</Role>
      <ShortName>PREMISES AND EQUIPMENT (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>4090 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureGoodwillAndIntangibleAssetsDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>4100 - Disclosure - DEPOSITS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureDepositsDetails</Role>
      <ShortName>DEPOSITS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>4110 - Disclosure - OTHER BORROWINGS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureOtherBorrowingsDetails</Role>
      <ShortName>OTHER BORROWINGS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>4120 - Disclosure - FEDERAL HOME LOAN BANK ADVANCES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureFederalHomeLoanBankAdvancesDetails</Role>
      <ShortName>FEDERAL HOME LOAN BANK ADVANCES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>4130 - Disclosure - SUBORDINATED DEBENTURES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSubordinatedDebenturesDetails</Role>
      <ShortName>SUBORDINATED DEBENTURES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>4140 - Disclosure - MORTGAGE BANKING AND LOAN SERVICING (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureMortgageBankingAndLoanServicingDetails</Role>
      <ShortName>MORTGAGE BANKING AND LOAN SERVICING (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>4141 - Disclosure - MORTGAGE BANKING AND LOAN SERVICING (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureMortgageBankingAndLoanServicingDetails2</Role>
      <ShortName>MORTGAGE BANKING AND LOAN SERVICING (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>4150 - Disclosure - INCOME TAX (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureIncomeTaxDetails</Role>
      <ShortName>INCOME TAX (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>4151 - Disclosure - INCOME TAX (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureIncomeTaxDetails2</Role>
      <ShortName>INCOME TAX (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>4152 - Disclosure - INCOME TAX (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureIncomeTaxDetails3</Role>
      <ShortName>INCOME TAX (Details 3)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>4160 - Disclosure - COMMITMENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureCommitmentsDetails</Role>
      <ShortName>COMMITMENTS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>4170 - Disclosure - DIVIDENDS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureDividendsDetails</Role>
      <ShortName>DIVIDENDS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>4190 - Disclosure - REGULATORY MATTERS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRegulatoryMattersDetails</Role>
      <ShortName>REGULATORY MATTERS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>4200 - Disclosure - EMPLOYEE BENEFIT PLANS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureEmployeeBenefitPlansDetails</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>4210 - Disclosure - RELATED PARTY TRANSACTIONS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureRelatedPartyTransactionsDetails</Role>
      <ShortName>RELATED PARTY TRANSACTIONS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>4220 - Disclosure - STOCK-BASED COMPENSATION (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureStockBasedCompensationDetails</Role>
      <ShortName>STOCK-BASED COMPENSATION (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>4221 - Disclosure - STOCK-BASED COMPENSATION (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureStockBasedCompensationDetails2</Role>
      <ShortName>STOCK-BASED COMPENSATION (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>4230 - Disclosure - EARNINGS PER COMMON SHARE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureEarningsPerCommonShareDetails</Role>
      <ShortName>EARNINGS PER COMMON SHARE (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>4240 - Disclosure - QUARTERLY FINANCIAL DATA (UNAUDITED) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureQuarterlyFinancialDataDetails</Role>
      <ShortName>QUARTERLY FINANCIAL DATA (UNAUDITED) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>4250 - Disclosure - PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureParentOnlyCondensedFinancialStatementsDetails</Role>
      <ShortName>PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>4251 - Disclosure - PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureParentOnlyCondensedFinancialStatementsDetails2</Role>
      <ShortName>PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>4252 - Disclosure - PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureParentOnlyCondensedFinancialStatementsDetails3</Role>
      <ShortName>PARENT ONLY CONDENSED FINANCIAL STATEMENTS (Details 3)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>4260 - Disclosure - ACQUISITIONS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureAcquisitionsDetails</Role>
      <ShortName>ACQUISITIONS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>4270 - Disclosure - SUBSEQUENT EVENT - BRANCH CLOSURES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainsourcefinancial.com/role/DisclosureSubsequentEventDetails</Role>
      <ShortName>SUBSEQUENT EVENT - BRANCH CLOSURES (Details)</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 msfg_LoansAndLeasesReceivableCommitmentsInterestRates had a mix of decimals attribute values: 3 4.</Log>
    <Log type="Info">Element us-gaap_CashAcquiredFromAcquisition had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_PreferredStockValue had a mix of decimals attribute values: -6 -3.</Log>
    <Log type="Info">'Monetary' elements on report '4020 - Disclosure - PREFERRED STOCK AND STOCK REPURCHASE (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '4056 - Disclosure - LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 7)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '4140 - Disclosure - MORTGAGE BANKING AND LOAN SERVICING (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '4260 - Disclosure - ACQUISITIONS (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 0010 - Statement - CONSOLIDATED BALANCE SHEETS</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2010'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2009'</Log>
    <Log type="Info">Process Flow-Through: 0015 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2010'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2009'</Log>
    <Log type="Info">Process Flow-Through: 0020 - Statement - CONSOLIDATED STATEMENTS OF INCOME</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2012'</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: Removing column '3 Months Ended
Dec. 31, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 0030 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2012'</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: Removing column '3 Months Ended
Dec. 31, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 0045 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 0050 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</Log>
  </Logs>
  <InputFiles>
    <File>msfg-20121231.xml</File>
    <File>msfg-20121231.xsd</File>
    <File>msfg-20121231_cal.xml</File>
    <File>msfg-20121231_def.xml</File>
    <File>msfg-20121231_lab.xml</File>
    <File>msfg-20121231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
