<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>566</ContextCount>
  <ElementCount>476</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>126</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>995200090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>995200100 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/StatementConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>995200105 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>995200200 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/StatementConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>995200300 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/StatementConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>995200400 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/StatementConsolidatedStatementsOfChangesInShareholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>995200405 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/StatementConsolidatedStatementsOfChangesInShareholdersEquityParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>995200500 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995210101 - Disclosure - BASIS OF PRESENTATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBasisOfPresentation</Role>
      <ShortName>BASIS OF PRESENTATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995210201 - Disclosure - ACQUISITION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureAcquisition</Role>
      <ShortName>ACQUISITION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995210301 - Disclosure - SECURITIES AVAILABLE FOR SALE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSale</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995210401 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLosses</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995210501 - Disclosure - BORROWED FUNDS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFunds</Role>
      <ShortName>BORROWED FUNDS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995210601 - Disclosure - DEPOSITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDeposits</Role>
      <ShortName>DEPOSITS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995210701 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquity</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995210801 - Disclosure - EARNINGS PER SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureEarningsPerShare</Role>
      <ShortName>EARNINGS PER SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995210901 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivities</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995211001 - Disclosure - FAIR VALUE MEASUREMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurements</Role>
      <ShortName>FAIR VALUE MEASUREMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995211101 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureRevenueFromContractsWithCustomers</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995211201 - Disclosure - GOODWILL AND OTHER INTANGIBLES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureGoodwillAndOtherIntangibles</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995211301 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLeases</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.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>22</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.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>23</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>99920102 - Disclosure - BASIS OF PRESENTATION (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBasisOfPresentationPolicies</Role>
      <ShortName>BASIS OF PRESENTATION (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>99930303 - Disclosure - SECURITIES AVAILABLE FOR SALE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleTables</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSale</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>99930403 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesTables</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLosses</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>99930503 - Disclosure - BORROWED FUNDS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFundsTables</Role>
      <ShortName>BORROWED FUNDS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureBorrowedFunds</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>99930603 - Disclosure - DEPOSITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDepositsTables</Role>
      <ShortName>DEPOSITS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureDeposits</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>99930703 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquityTables</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquity</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>99930803 - Disclosure - EARNINGS PER SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureEarningsPerShareTables</Role>
      <ShortName>EARNINGS PER SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureEarningsPerShare</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>99930903 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesTables</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivities</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>99931003 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>99931103 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureRevenueFromContractsWithCustomersTables</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureRevenueFromContractsWithCustomers</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>99931203 - Disclosure - GOODWILL AND OTHER INTANGIBLES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureGoodwillAndOtherIntangiblesTables</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureGoodwillAndOtherIntangibles</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>99931303 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLeasesTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureLeases</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>99940101 - Disclosure - BASIS OF PRESENTATION (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBasisOfPresentationDetails</Role>
      <ShortName>BASIS OF PRESENTATION (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureBasisOfPresentationPolicies</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>99940201 - Disclosure - ACQUISITION - (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureAcquisitionDetails</Role>
      <ShortName>ACQUISITION - (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureAcquisition</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>99940301 - Disclosure - SECURITIES AVAILABLE FOR SALE - Summary of Available-for-Sale debt securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleSummaryOfAvailableForSaleDebtSecuritiesDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Summary of Available-for-Sale debt securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>99940302 - Disclosure - SECURITIES AVAILABLE FOR SALE - Allowance for Credit Losses on Available-for-Sale Debt Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleAllowanceForCreditLossesOnAvailableForSaleDebtSecuritiesDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Allowance for Credit Losses on Available-for-Sale Debt Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>99940303 - Disclosure - SECURITIES AVAILABLE FOR SALE - Maturities of Available for Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleMaturitiesOfAvailableForSaleSecuritiesDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Maturities of Available for Sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>99940304 - Disclosure - SECURITIES AVAILABLE FOR SALE - Summary of Securities with Unrealized Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleSummaryOfSecuritiesWithUnrealizedLossesDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Summary of Securities with Unrealized Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>99940305 - Disclosure - SECURITIES AVAILABLE FOR SALE - Proceeds from Sales, Calls and Maturities of Available-for-Sale Debt Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleProceedsFromSalesCallsAndMaturitiesOfAvailableForSaleDebtSecuritiesDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Proceeds from Sales, Calls and Maturities of Available-for-Sale Debt Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>99940306 - Disclosure - SECURITIES AVAILABLE FOR SALE - Basis for Impairment Conclusion (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleBasisForImpairmentConclusionDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Basis for Impairment Conclusion (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>99940307 - Disclosure - SECURITIES AVAILABLE FOR SALE - Securities Pledged for Collateral (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureSecuritiesAvailableForSaleSecuritiesPledgedForCollateralDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Securities Pledged for Collateral (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>99940401 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Summary of Total Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesSummaryOfTotalLoansDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Summary of Total Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>99940402 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Unamortized Net Costs and Premiums (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesUnamortizedNetCostsAndPremiumsDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Unamortized Net Costs and Premiums (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>99940403 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Allowance Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesAllowanceActivityDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Allowance Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>99940404 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loans by Year of Origination, Loan Segmentation and Risk Indicator (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesLoansByYearOfOriginationLoanSegmentationAndRiskIndicatorDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loans by Year of Origination, Loan Segmentation and Risk Indicator (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>99940405 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Summary of Past Due Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesSummaryOfPastDueLoansDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Summary of Past Due Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>99940406 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Non-accrual Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesNonAccrualLoansDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Non-accrual Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>99940407 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Amortized Cost Basis of Collateral Dependent Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesAmortizedCostBasisOfCollateralDependentLoansDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Amortized Cost Basis of Collateral Dependent Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>99940408 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loan Modifications (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesLoanModificationsDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loan Modifications (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>99940409 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - PCD Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesPcdLoansDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - PCD Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>99940410 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES - Mortgage Banking (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLoansAndAllowanceForCreditLossesMortgageBankingDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES - Mortgage Banking (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>99940501 - Disclosure - BORROWED FUNDS - Summary of Borrowed Funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFundsSummaryOfBorrowedFundsDetails</Role>
      <ShortName>BORROWED FUNDS - Summary of Borrowed Funds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>99940502 - Disclosure - BORROWED FUNDS - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFundsAdditionalInformationDetails</Role>
      <ShortName>BORROWED FUNDS - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>99940503 - Disclosure - BORROWED FUNDS - Maturities of FHLB Advances (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFundsMaturitiesOfFhlbAdvancesDetails</Role>
      <ShortName>BORROWED FUNDS - Maturities of FHLB Advances (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>99940504 - Disclosure - BORROWED FUNDS - Subordinated and Junior Subordinated Borrowings (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFundsSubordinatedAndJuniorSubordinatedBorrowingsNarrativeDetails</Role>
      <ShortName>BORROWED FUNDS - Subordinated and Junior Subordinated Borrowings (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>99940505 - Disclosure - BORROWED FUNDS - Subordinated Borrowings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFundsSubordinatedBorrowingsDetails</Role>
      <ShortName>BORROWED FUNDS - Subordinated Borrowings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>99940506 - Disclosure - BORROWED FUNDS - Repurchase Agreements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureBorrowedFundsRepurchaseAgreementsDetails</Role>
      <ShortName>BORROWED FUNDS - Repurchase Agreements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>99940601 - Disclosure - DEPOSITS - Components (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDepositsComponentsDetails</Role>
      <ShortName>DEPOSITS - Components (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>99940602 - Disclosure - DEPOSITS - Maturities, Brokered, Reciprocal (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDepositsMaturitiesBrokeredReciprocalDetails</Role>
      <ShortName>DEPOSITS - Maturities, Brokered, Reciprocal (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>99940701 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Actual and Required Capital Ratios (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquityActualAndRequiredCapitalRatiosDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Actual and Required Capital Ratios (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>99940702 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of AOCIL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquityComponentsOfAocilDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of AOCIL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>99940703 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of OCIL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquityComponentsOfOcilDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of OCIL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>99940704 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Changes in AOCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquityChangesInAociDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Changes in AOCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>99940705 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Amounts Reclassified Out of AOCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureCapitalRatiosAndShareholdersEquityAmountsReclassifiedOutOfAociDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Amounts Reclassified Out of AOCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>99940801 - Disclosure - EARNINGS PER SHARE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureEarningsPerShareDetails</Role>
      <ShortName>EARNINGS PER SHARE (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureEarningsPerShareTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>99940901 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>99940902 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Amount of Gain (Loss) recognized in Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesAmountOfGainLossRecognizedInOtherComprehensiveIncomeDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Amount of Gain (Loss) recognized in Other Comprehensive Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>99940903 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Effect of cash flow hedging and fair value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesEffectOfCashFlowHedgingAndFairValueDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Effect of cash flow hedging and fair value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>99940904 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Consolidated statements of income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesConsolidatedStatementsOfIncomeDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Consolidated statements of income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>99940905 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesAdditionalInformationDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>99940906 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Offsetting Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureDerivativeFinancialInstrumentsAndHedgingActivitiesOffsettingAssetsAndLiabilitiesDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Offsetting Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>99941001 - Disclosure - FAIR VALUE MEASUREMENTS - Measured on Recurring And Non Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurementsMeasuredOnRecurringAndNonRecurringBasisDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Measured on Recurring And Non Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>99941002 - Disclosure - FAIR VALUE MEASUREMENTS - Corporate Bonds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurementsCorporateBondsDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Corporate Bonds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>99941003 - Disclosure - FAIR VALUE MEASUREMENTS - Changes in Level 3 (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurementsChangesInLevel3Details</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Changes in Level 3 (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>99941004 - Disclosure - FAIR VALUE MEASUREMENTS - Unobservable Inputs Recurring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurementsUnobservableInputsRecurringDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Unobservable Inputs Recurring (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>99941005 - Disclosure - FAIR VALUE MEASUREMENTS - Unobservable Inputs Non-recurring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurementsUnobservableInputsNonRecurringDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Unobservable Inputs Non-recurring (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>99941006 - Disclosure - FAIR VALUE MEASUREMENTS - Fair Values and Carrying Amounts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureFairValueMeasurementsFairValuesAndCarryingAmountsDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Fair Values and Carrying Amounts (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>99941101 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation of Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureRevenueFromContractsWithCustomersDisaggregationOfRevenueDetails</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation of Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>99941102 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Contract Balances from Contracts with Customers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureRevenueFromContractsWithCustomersContractBalancesFromContractsWithCustomersDetails</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS - Contract Balances from Contracts with Customers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>99941201 - Disclosure - GOODWILL AND OTHER INTANGIBLES - Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureGoodwillAndOtherIntangiblesGoodwillDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES - Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>99941202 - Disclosure - GOODWILL AND OTHER INTANGIBLES - Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureGoodwillAndOtherIntangiblesIntangibleAssetsDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES - Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>99941301 - Disclosure - LEASES - Assets and liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLeasesAssetsAndLiabilitiesDetails</Role>
      <ShortName>LEASES - Assets and liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>99941302 - Disclosure - LEASES - Lease Term and Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLeasesLeaseTermAndCostDetails</Role>
      <ShortName>LEASES - Lease Term and Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="bhb-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>99941303 - Disclosure - LEASES - Future Minimum Payments for Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DisclosureLeasesFutureMinimumPaymentsForLeasesDetails</Role>
      <ShortName>LEASES - Future Minimum Payments for Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>bhb-20260331.xsd</File>
    <File>bhb-20260331_cal.xml</File>
    <File>bhb-20260331_def.xml</File>
    <File>bhb-20260331_lab.xml</File>
    <File>bhb-20260331_pre.xml</File>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="bhb-20260331x10q.htm">bhb-20260331x10q.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>bhb-20260331x10q001.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1827">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
