<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.3.1.900</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>406</ContextCount>
  <ElementCount>312</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>78</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfFinancialCondition</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfFinancialConditionParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1002501 - Statement - CONSOLIDATED STATEMENTS OF INCOME (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfIncomeParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004000 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfShareholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1004501 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfShareholdersEquityParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>1005000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/AccountingPolicies</Role>
      <ShortName>Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Recent Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/RecentAccountingPronouncements</Role>
      <ShortName>Recent Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Investment Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/InvestmentSecurities</Role>
      <ShortName>Investment Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Loan and Lease Financings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/LoanAndLeaseFinancings</Role>
      <ShortName>Loan and Lease Financings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Reserve for Loan and Lease Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ReserveForLoanAndLeaseLosses</Role>
      <ShortName>Reserve for Loan and Lease Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Mortgage Servicing Rights</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/MortgageServicingRights</Role>
      <ShortName>Mortgage Servicing Rights</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Commitments and Financial Instruments with Off-Balance-Sheet Risk</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/CommitmentsAndFinancialInstrumentsWithOffBalanceSheetRisk</Role>
      <ShortName>Commitments and Financial Instruments with Off-Balance-Sheet Risk</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Derivative Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DerivativeFinancialInstruments</Role>
      <ShortName>Derivative Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Stock Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/StockBasedCompensation</Role>
      <ShortName>Stock Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Accumulated Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/AccumulatedOtherComprehensiveIncome</Role>
      <ShortName>Accumulated Other Comprehensive Income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Accounting Policies Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/AccountingPoliciesAccountingPoliciesPolicies</Role>
      <ShortName>Accounting Policies Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/AccountingPolicies</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Investment Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/InvestmentSecuritiesTables</Role>
      <ShortName>Investment Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/InvestmentSecurities</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Loan and Lease Financings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/LoanAndLeaseFinancingsTables</Role>
      <ShortName>Loan and Lease Financings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/LoanAndLeaseFinancings</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Reserve for Loan and Lease Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ReserveForLoanAndLeaseLossesTables</Role>
      <ShortName>Reserve for Loan and Lease Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/ReserveForLoanAndLeaseLosses</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - Mortgage Servicing Rights (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/MortgageServicingRightsTables</Role>
      <ShortName>Mortgage Servicing Rights (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/MortgageServicingRights</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Commitments and Financial Instruments with Off-Balance-Sheet Risk (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/CommitmentsAndFinancialInstrumentsWithOffBalanceSheetRiskTables</Role>
      <ShortName>Commitments and Financial Instruments with Off-Balance-Sheet Risk (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/CommitmentsAndFinancialInstrumentsWithOffBalanceSheetRisk</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Derivative Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DerivativeFinancialInstrumentsTables</Role>
      <ShortName>Derivative Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/DerivativeFinancialInstruments</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/EarningsPerShare</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - Accumulated Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/AccumulatedOtherComprehensiveIncomeTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/AccumulatedOtherComprehensiveIncome</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurements</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - Accounting Policies Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/AccountingPoliciesAccountingPoliciesDetails</Role>
      <ShortName>Accounting Policies Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/AccountingPoliciesAccountingPoliciesPolicies</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Investment Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/InvestmentSecuritiesDetails</Role>
      <ShortName>Investment Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Investment Securities (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/InvestmentSecuritiesDetails2</Role>
      <ShortName>Investment Securities (Details 2)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Loan and Lease Financings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/LoanAndLeaseFinancingsDetails</Role>
      <ShortName>Loan and Lease Financings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/LoanAndLeaseFinancingsTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Loan and Lease Financings (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/LoanAndLeaseFinancingsDetails2</Role>
      <ShortName>Loan and Lease Financings (Details 2)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/LoanAndLeaseFinancingsTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Loan and Lease Financings (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/LoanAndLeaseFinancingsDetails3</Role>
      <ShortName>Loan and Lease Financings (Details 3)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/LoanAndLeaseFinancingsTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Loan and Lease Financings (Details 4)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/LoanAndLeaseFinancingsDetails4</Role>
      <ShortName>Loan and Lease Financings (Details 4)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/LoanAndLeaseFinancingsTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2404406 - Disclosure - Loan and Lease Financings (Details 5)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/LoanAndLeaseFinancingsDetails5</Role>
      <ShortName>Loan and Lease Financings (Details 5)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/LoanAndLeaseFinancingsTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Reserve for Loan and Lease Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/ReserveForLoanAndLeaseLossesDetails</Role>
      <ShortName>Reserve for Loan and Lease Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/ReserveForLoanAndLeaseLossesTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Mortgage Servicing Rights (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/MortgageServicingRightsDetails</Role>
      <ShortName>Mortgage Servicing Rights (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/MortgageServicingRightsTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2406403 - Disclosure - Mortgage Servicing Rights (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/MortgageServicingRightsDetails2</Role>
      <ShortName>Mortgage Servicing Rights (Details 2)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/MortgageServicingRightsTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Commitments and Financial Instruments with Off-Balance-Sheet Risk (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/CommitmentsAndFinancialInstrumentsWithOffBalanceSheetRiskDetails</Role>
      <ShortName>Commitments and Financial Instruments with Off-Balance-Sheet Risk (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/CommitmentsAndFinancialInstrumentsWithOffBalanceSheetRiskTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - Commitments and Financial Instruments with Off-Balance-Sheet Risk (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/CommitmentsAndFinancialInstrumentsWithOffBalanceSheetRiskDetails2</Role>
      <ShortName>Commitments and Financial Instruments with Off-Balance-Sheet Risk (Details 2)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/CommitmentsAndFinancialInstrumentsWithOffBalanceSheetRiskTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Derivative Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DerivativeFinancialInstrumentsDetails</Role>
      <ShortName>Derivative Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/DerivativeFinancialInstrumentsTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/EarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/EarningsPerShareTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Derivative Financial Instruments (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DerivativeFinancialInstrumentsDetails2</Role>
      <ShortName>Derivative Financial Instruments (Details 2)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/DerivativeFinancialInstrumentsTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2408404 - Disclosure - Derivative Financial Instruments (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DerivativeFinancialInstrumentsDetails3</Role>
      <ShortName>Derivative Financial Instruments (Details 3)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/DerivativeFinancialInstrumentsTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2408405 - Disclosure - Derivative Financial Instruments (Details 4)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DerivativeFinancialInstrumentsDetails4</Role>
      <ShortName>Derivative Financial Instruments (Details 4)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/DerivativeFinancialInstrumentsTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2408406 - Disclosure - Derivative Financial Instruments (Details 5)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/DerivativeFinancialInstrumentsDetails5</Role>
      <ShortName>Derivative Financial Instruments (Details 5)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/DerivativeFinancialInstrumentsTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Stock Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/StockBasedCompensationDetails</Role>
      <ShortName>Stock Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/StockBasedCompensation</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Accumulated Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/AccumulatedOtherComprehensiveIncomeDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/AccumulatedOtherComprehensiveIncomeTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2413401 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/IncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/IncomeTaxes</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Fair Value Measurements (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsDetails2</Role>
      <ShortName>Fair Value Measurements (Details 2)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2414404 - Disclosure - Fair Value Measurements (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsDetails3</Role>
      <ShortName>Fair Value Measurements (Details 3)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2414405 - Disclosure - Fair Value Measurements (Details 4)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsDetails4</Role>
      <ShortName>Fair Value Measurements (Details 4)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2414406 - Disclosure - Fair Value Measurements (Details 5)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsDetails5</Role>
      <ShortName>Fair Value Measurements (Details 5)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2414407 - Disclosure - Fair Value Measurements (Details 6)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsDetails6</Role>
      <ShortName>Fair Value Measurements (Details 6)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="srce-20160331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2414408 - Disclosure - Fair Value Measurements (Details 7)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.1stsource.com/role/FairValueMeasurementsDetails7</Role>
      <ShortName>Fair Value Measurements (Details 7)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.1stsource.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>srce-20160331.xml</File>
    <File>srce-20160331.xsd</File>
    <File>srce-20160331_cal.xml</File>
    <File>srce-20160331_def.xml</File>
    <File>srce-20160331_lab.xml</File>
    <File>srce-20160331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies/>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
