<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>464</ContextCount>
  <ElementCount>449</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>102</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>75000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>75010 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_StatementConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>75020 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>75030 - Statement - Consolidated Statements of Operations (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_StatementConsolidatedStatementsOfOperationsUnaudited</Role>
      <ShortName>Consolidated Statements of Operations (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>75040 - Statement - Consolidated Statements of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncomeUnaudited</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>75050 - Statement - Consolidated Statement of Changes in Shareholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_StatementConsolidatedStatementOfChangesInShareholdersEquityUnaudited</Role>
      <ShortName>Consolidated Statement of Changes in Shareholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>75060 - Statement - Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_StatementConsolidatedStatementOfChangesInShareholdersEquityUnauditedParenthetical</Role>
      <ShortName>Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>75070 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995455 - Disclosure - Consolidated Financial Statements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureConsolidatedFinancialStatements</Role>
      <ShortName>Consolidated Financial Statements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995465 - Disclosure - Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSignificantAccountingPolicies</Role>
      <ShortName>Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995475 - Disclosure - Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSecurities</Role>
      <ShortName>Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995485 - Disclosure - Loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureLoans</Role>
      <ShortName>Loans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995495 - Disclosure - Allowance for Credit Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLosses1</Role>
      <ShortName>Allowance for Credit Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995505 - Disclosure - Accumulated Other Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995515 - Disclosure - Goodwill and Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssets</Role>
      <ShortName>Goodwill and Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995525 - Disclosure - Short-Term and Other Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureShortTermAndOtherBorrowings</Role>
      <ShortName>Short-Term and Other Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995535 - Disclosure - Earnings per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEarningsPerCommonShare</Role>
      <ShortName>Earnings per Common Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995545 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Risk</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureCommitmentsContingenciesAndOffBalanceSheetRisk</Role>
      <ShortName>Commitments, Contingencies and Off-Balance Sheet Risk</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995555 - Disclosure - Pension Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosurePensionInformation</Role>
      <ShortName>Pension Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995565 - Disclosure - Equity Incentive Plan</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEquityIncentivePlan</Role>
      <ShortName>Equity Incentive Plan</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995575 - Disclosure - Fair Value Measurement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurement</Role>
      <ShortName>Fair Value Measurement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995585 - Disclosure - Derivatives</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureDerivatives</Role>
      <ShortName>Derivatives</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995595 - Disclosure - Qualified Affordable Housing Project Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureQualifiedAffordableHousingProjectInvestments</Role>
      <ShortName>Qualified Affordable Housing Project Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995605 - Disclosure - Revenue Recognition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureRevenueRecognition</Role>
      <ShortName>Revenue Recognition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995615 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLeases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995625 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureSegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995635 - Disclosure - Acquisitions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAcquisitions</Role>
      <ShortName>Acquisitions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995655 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSignificantAccountingPolicies</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995675 - Disclosure - Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSecuritiesTables</Role>
      <ShortName>Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSecurities</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995685 - Disclosure - Loans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureLoansTables</Role>
      <ShortName>Loans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureLoans</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995695 - Disclosure - Allowance for Credit Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesTables</Role>
      <ShortName>Allowance for Credit Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLosses1</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995705 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/DisclosureAccumulatedOtherComprehensiveIncomeLoss</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995715 - Disclosure - Goodwill and Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsTables</Role>
      <ShortName>Goodwill and Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssets</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995725 - Disclosure - Short-Term and Other Borrowings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureShortTermAndOtherBorrowingsTables</Role>
      <ShortName>Short-Term and Other Borrowings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureShortTermAndOtherBorrowings</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995735 - Disclosure - Earnings per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEarningsPerCommonShareTables</Role>
      <ShortName>Earnings per Common Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEarningsPerCommonShare</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995745 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Risk (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureCommitmentsContingenciesAndOffBalanceSheetRiskTables</Role>
      <ShortName>Commitments, Contingencies and Off-Balance Sheet Risk (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureCommitmentsContingenciesAndOffBalanceSheetRisk</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995755 - Disclosure - Pension Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosurePensionInformationTables</Role>
      <ShortName>Pension Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosurePensionInformation</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995765 - Disclosure - Equity Incentive Plan (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEquityIncentivePlanTables</Role>
      <ShortName>Equity Incentive Plan (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEquityIncentivePlan</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995775 - Disclosure - Fair Value Measurement (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurementTables</Role>
      <ShortName>Fair Value Measurement (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurement</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995785 - Disclosure - Derivatives (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureDerivativesTables</Role>
      <ShortName>Derivatives (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureDerivatives</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995795 - Disclosure - Revenue Recognition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureRevenueRecognitionTables</Role>
      <ShortName>Revenue Recognition (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureRevenueRecognition</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995805 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/DisclosureLeases</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995815 - Disclosure - Acquisitions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAcquisitionsTables</Role>
      <ShortName>Acquisitions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/DisclosureAcquisitions</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995825 - Disclosure - Consolidated Financial Statements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureConsolidatedFinancialStatementsAdditionalInformationDetails</Role>
      <ShortName>Consolidated Financial Statements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>995835 - Disclosure - Significant Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Significant Accounting Policies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>995855 - Disclosure - Securities - Available for Sale Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleSecuritiesDetail</Role>
      <ShortName>Securities - Available for Sale Securities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>995865 - Disclosure - Securities - Available for Sale Securities (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureSecuritiesAvailableForSaleSecuritiesParentheticalDetails</Role>
      <ShortName>Securities - Available for Sale Securities (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>995875 - Disclosure - Securities - Amortized Cost and Fair Value of Debt Securities by Contractual Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureSecuritiesAmortizedCostAndFairValueOfDebtSecuritiesByContractualMaturityDetail</Role>
      <ShortName>Securities - Amortized Cost and Fair Value of Debt Securities by Contractual Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>995885 - Disclosure - Securities - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAdditionalInformationDetail</Role>
      <ShortName>Securities - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>995895 - Disclosure - Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureSecuritiesGrossUnrealizedLossesAndFairValueAggregatedByInvestmentCategoryDetail</Role>
      <ShortName>Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>995905 - Disclosure - Securities - Schedule of Net Gains and Losses on Equity Investments Recognized in Earnings and Portion of Unrealized Gains and Losses for Period that Relates to Equity Investments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureSecuritiesScheduleOfNetGainsAndLossesOnEquityInvestmentsRecognizedInEarningsAndPortionOfUnrealizedGainsAndLossesForPeriodThat</Role>
      <ShortName>Securities - Schedule of Net Gains and Losses on Equity Investments Recognized in Earnings and Portion of Unrealized Gains and Losses for Period that Relates to Equity Investments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>995915 - Disclosure - Loans - Loan Balances (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureLoansLoanBalancesDetail</Role>
      <ShortName>Loans - Loan Balances (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>995925 - Disclosure - Loans - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureLoansAdditionalInformationDetail</Role>
      <ShortName>Loans - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>995935 - Disclosure - Loans - Schedule of Net Investment in Direct financing and Sales-type leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLoansScheduleOfNetInvestmentInDirectFinancingAndSalestypeLeasesDetails</Role>
      <ShortName>Loans - Schedule of Net Investment in Direct financing and Sales-type leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>995945 - Disclosure - Loans - Schedule of Components of Lease Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLoansScheduleOfComponentsOfLeaseIncomeDetails</Role>
      <ShortName>Loans - Schedule of Components of Lease Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>995955 - Disclosure - Allowance for Credit Losses - Changes in the Allowance for Credit Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesChangesInTheAllowanceForCreditLossesDetail</Role>
      <ShortName>Allowance for Credit Losses - Changes in the Allowance for Credit Losses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>995965 - Disclosure - Allowance for Credit Losses - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesAdditionalInformationDetail</Role>
      <ShortName>Allowance for Credit Losses - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>995975 - Disclosure - Allowance for Credit Losses - Based On the Most Recent Analysis Performed, the Risk Category of Loans, By Type and Year of Originations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesBasedOnTheMostRecentAnalysisPerformedTheRiskCategoryOfLoansByTypeAndYearOfOriginationsDetails</Role>
      <ShortName>Allowance for Credit Losses - Based On the Most Recent Analysis Performed, the Risk Category of Loans, By Type and Year of Originations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>995995 - Disclosure - Allowance for Credit Losses - Aging Analysis of Past Due Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesAgingAnalysisOfPastDueLoansDetail</Role>
      <ShortName>Allowance for Credit Losses - Aging Analysis of Past Due Loans (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>996005 - Disclosure - Allowance for Credit Losses - Summary of Nonaccrual Loans Excluding Purchased Credit-Impaired (PCI) Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesSummaryOfNonaccrualLoansExcludingPurchasedCreditimpairedPciLoansDetail</Role>
      <ShortName>Allowance for Credit Losses - Summary of Nonaccrual Loans Excluding Purchased Credit-Impaired (PCI) Loans (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>996015 - Disclosure - Allowance for Credit Losses - Schedule of Loans Modified to Borrowers Experiencing Financial Difficulty (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesScheduleOfLoansModifiedToBorrowersExperiencingFinancialDifficultyDetails</Role>
      <ShortName>Allowance for Credit Losses - Schedule of Loans Modified to Borrowers Experiencing Financial Difficulty (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>996025 - Disclosure - Allowance for Credit Losses - Schedule of Amortized Cost Basis of Collateral Dependent Loans Individually Evaluated Expected Credit Losses and Related Allowance for Credit Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesScheduleOfAmortizedCostBasisOfCollateralDependentLoansIndividuallyEvaluatedExpectedCreditLossesAndRelate</Role>
      <ShortName>Allowance for Credit Losses - Schedule of Amortized Cost Basis of Collateral Dependent Loans Individually Evaluated Expected Credit Losses and Related Allowance for Credit Losses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>996035 - Disclosure - Allowance for Credit Losses - Schedule Of Allowance For Credit Losses On Off-balance Sheet Credit Exposures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAllowanceForCreditLossesScheduleOfAllowanceForCreditLossesOnOffbalanceSheetCreditExposuresDetails</Role>
      <ShortName>Allowance for Credit Losses - Schedule Of Allowance For Credit Losses On Off-balance Sheet Credit Exposures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>996045 - Disclosure - Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAccumulatedOtherComprehensiveIncomeLossChangesInEachComponentOfAccumulatedOtherComprehensiveIncomeLossNetOfTaxDetail</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/DisclosureAccumulatedOtherComprehensiveIncomeLossTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>996055 - Disclosure - Accumulated Other Comprehensive Income (Loss) - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAccumulatedOtherComprehensiveIncomeLossAdditionalInformationDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss) - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.civb.com/20260331/taxonomy/role/DisclosureAccumulatedOtherComprehensiveIncomeLossTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>996065 - Disclosure - Goodwill and Intangible Assets - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsAdditionalInformationDetail</Role>
      <ShortName>Goodwill and Intangible Assets - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>996075 - Disclosure - Goodwill and Intangible Assets - Schedule of Acquired Intangible Assets, Other than Goodwill (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsScheduleOfAcquiredIntangibleAssetsOtherThanGoodwillDetail</Role>
      <ShortName>Goodwill and Intangible Assets - Schedule of Acquired Intangible Assets, Other than Goodwill (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>996085 - Disclosure - Goodwill and Intangible Assets - Schedule of Mortgage Servicing Rights (MSRs) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsScheduleOfMortgageServicingRightsMsrsDetail</Role>
      <ShortName>Goodwill and Intangible Assets - Schedule of Mortgage Servicing Rights (MSRs) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>996095 - Disclosure - Goodwill and Intangible Assets - Schedule of Estimated Amortization Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureGoodwillAndIntangibleAssetsScheduleOfEstimatedAmortizationExpenseDetail</Role>
      <ShortName>Goodwill and Intangible Assets - Schedule of Estimated Amortization Expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>996105 - Disclosure - Short-Term and Other Borrowings - Summary of Federal Funds Purchased, Securities Sold Under Agreements to Repurchase and Other Short-term Borrowings (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureShortTermAndOtherBorrowingsSummaryOfFederalFundsPurchasedSecuritiesSoldUnderAgreementsToRepurchaseAndOtherShortTermBorrowingsDetail</Role>
      <ShortName>Short-Term and Other Borrowings - Summary of Federal Funds Purchased, Securities Sold Under Agreements to Repurchase and Other Short-term Borrowings (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>996115 - Disclosure - Short-Term and Other Borrowings - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureShorttermAndOtherBorrowingsAdditionalInformationDetails</Role>
      <ShortName>Short-Term and Other Borrowings - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>996125 - Disclosure - Earnings per Common Share - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEarningsPerCommonShareAdditionalInformationDetail</Role>
      <ShortName>Earnings per Common Share - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>996135 - Disclosure - Earnings per Common Share - Computation of Basic and Diluted Earnings per Common Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEarningsPerCommonShareComputationOfBasicAndDilutedEarningsPerCommonShareDetail</Role>
      <ShortName>Earnings per Common Share - Computation of Basic and Diluted Earnings per Common Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>996145 - Disclosure - Commitments, Contingencies and Off-Balance-Sheet Risk - Contractual Amounts of Financial Instruments with Off-Balance-Sheet Risk (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureCommitmentsContingenciesAndOffBalanceSheetRiskContractualAmountsOfFinancialInstrumentsWithOffBalanceSheetRiskDetail</Role>
      <ShortName>Commitments, Contingencies and Off-Balance-Sheet Risk - Contractual Amounts of Financial Instruments with Off-Balance-Sheet Risk (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>996155 - Disclosure - Commitments, Contingencies and Off-Balance-Sheet Risk - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureCommitmentsContingenciesAndOffBalanceSheetRiskAdditionalInformationDetail</Role>
      <ShortName>Commitments, Contingencies and Off-Balance-Sheet Risk - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>996165 - Disclosure - Pension Information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosurePensionInformationAdditionalInformationDetail</Role>
      <ShortName>Pension Information - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>996175 - Disclosure - Pension Information - Components of Net Periodic Pension Cost (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosurePensionInformationComponentsOfNetPeriodicPensionCostDetail</Role>
      <ShortName>Pension Information - Components of Net Periodic Pension Cost (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>996185 - Disclosure - Equity Incentive Plan - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureEquityIncentivePlanAdditionalInformationDetail</Role>
      <ShortName>Equity Incentive Plan - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>996195 - Disclosure - Equity Incentive Plan - Summary of Company's Outstanding Restricted Common Stock (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureEquityIncentivePlanSummaryOfCompanysOutstandingRestrictedCommonStockDetail</Role>
      <ShortName>Equity Incentive Plan - Summary of Company's Outstanding Restricted Common Stock (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>996205 - Disclosure - Fair Value Measurement - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureFairValueMeasurementAdditionalInformationDetails</Role>
      <ShortName>Fair Value Measurement - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>996215 - Disclosure - Fair Value Measurement - Assets and Liabilities Measured at Fair Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurementAssetsAndLiabilitiesMeasuredAtFairValueDetail</Role>
      <ShortName>Fair Value Measurement - Assets and Liabilities Measured at Fair Value (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>996225 - Disclosure - Fair Value Measurement - Quantitative Information about Level 3 Fair Value Measurements (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurementQuantitativeInformationAboutLevel3FairValueMeasurementsDetail</Role>
      <ShortName>Fair Value Measurement - Quantitative Information about Level 3 Fair Value Measurements (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>996235 - Disclosure - Fair Value Measurement - Carrying Amount and Fair Value of Financial Instruments Not Measured at Fair Value on a Recurring or Nonrecurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurementCarryingAmountAndFairValueOfFinancialInstrumentsNotMeasuredAtFairValueOnRecurringOrNonrecurringBasisDetail</Role>
      <ShortName>Fair Value Measurement - Carrying Amount and Fair Value of Financial Instruments Not Measured at Fair Value on a Recurring or Nonrecurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>996245 - Disclosure - Derivatives - Summary of Interest Rate Swap (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureDerivativesSummaryOfInterestRateSwapDetails</Role>
      <ShortName>Derivatives - Summary of Interest Rate Swap (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>996255 - Disclosure - Derivatives - Summary of Interest Rate Swap Transactions (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureDerivativesSummaryOfInterestRateSwapTransactionsDetail</Role>
      <ShortName>Derivatives - Summary of Interest Rate Swap Transactions (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>996265 - Disclosure - Derivatives - Summary of Gross Notional Amount Derivatives (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureDerivativesSummaryOfGrossNotionalAmountDerivativesDetail</Role>
      <ShortName>Derivatives - Summary of Gross Notional Amount Derivatives (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>996275 - Disclosure - Derivatives - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureDerivativesAdditionalInformationDetail</Role>
      <ShortName>Derivatives - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>996285 - Disclosure - Qualified Affordable Housing Project Investments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureQualifiedAffordableHousingProjectInvestmentsAdditionalInformationDetail</Role>
      <ShortName>Qualified Affordable Housing Project Investments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>996295 - Disclosure - Revenue Recognition - Summary of Noninterest Income Segregated By Revenue Streams In-scope and Out-of-scope of Topic 606 (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/Role_DisclosureRevenueRecognitionSummaryOfNoninterestIncomeSegregatedByRevenueStreamsInScopeAndOutOfScopeOfTopic606Detail</Role>
      <ShortName>Revenue Recognition - Summary of Noninterest Income Segregated By Revenue Streams In-scope and Out-of-scope of Topic 606 (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>996305 - Disclosure - Leases - Summary of Balance Sheet Information Related to Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLeasesSummaryOfBalanceSheetInformationRelatedToOperatingLeasesDetails</Role>
      <ShortName>Leases - Summary of Balance Sheet Information Related to Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>996315 - Disclosure - Leases - Summary of Cost Components of Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLeasesSummaryOfCostComponentsOfOperatingLeasesDetails</Role>
      <ShortName>Leases - Summary of Cost Components of Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>996325 - Disclosure - Leases - Summary of Maturity of Operating Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLeasesSummaryOfMaturityOfOperatingLeaseLiabilitiesDetails</Role>
      <ShortName>Leases - Summary of Maturity of Operating Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>996345 - Disclosure - Leases - Summary of Weighted Average Remaining Lease Terms And Discount Rates For Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLeasesSummaryOfWeightedAverageRemainingLeaseTermsAndDiscountRatesForOperatingLeasesDetails</Role>
      <ShortName>Leases - Summary of Weighted Average Remaining Lease Terms And Discount Rates For Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>996355 - Disclosure - Leases - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureLeasesAdditionalInformationDetails</Role>
      <ShortName>Leases - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>996365 - Disclosure - Segment Reporting - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureSegmentReportingAdditionalInformationDetails</Role>
      <ShortName>Segment Reporting - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>996375 - Disclosure - Subsequent Events - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetails</Role>
      <ShortName>Subsequent Events - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>996385 - Disclosure - Acquisitions - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAcquisitionsAdditionalInformationDetails</Role>
      <ShortName>Acquisitions - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>996395 - Disclosure - Acquisitions - Schedule of Estimated Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAcquisitionsScheduleOfEstimatedAmortizationExpenseDetails</Role>
      <ShortName>Acquisitions - Schedule of Estimated Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>996405 - Disclosure - Acquisitions - Summary of Estimated Fair Values of the Assets Acquired and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAcquisitionsSummaryOfEstimatedFairValuesOfTheAssetsAcquiredAndLiabilitiesDetails</Role>
      <ShortName>Acquisitions - Summary of Estimated Fair Values of the Assets Acquired and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="civb-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>996415 - Disclosure - Acquisitions - Summary of Estimated Fair Values of the Assets Acquired and Liabilities (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.civb.com/20260331/taxonomy/role/DisclosureAcquisitionsSummaryOfEstimatedFairValuesOfTheAssetsAcquiredAndLiabilitiesParentheticalDetails</Role>
      <ShortName>Acquisitions - Summary of Estimated Fair Values of the Assets Acquired and Liabilities (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="civb-20260331.htm">civb-20260331.htm</File>
    <File>civb-20260331.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1561">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
