<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.19.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>995</ContextCount>
  <ElementCount>442</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>119</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004000 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/ConsolidatedStatementsOfChangesInShareholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004501 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/ConsolidatedStatementsOfChangesInShareholdersEquityParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1005000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - BASIS OF PRESENTATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BasisOfPresentation</Role>
      <ShortName>BASIS OF PRESENTATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - SECURITIES AVAILABLE FOR SALE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SecuritiesAvailableForSale</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - LOANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/Loans</Role>
      <ShortName>LOANS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - ALLOWANCE FOR LOAN LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/AllowanceForLoanLosses</Role>
      <ShortName>ALLOWANCE FOR LOAN LOSSES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - BORROWED FUNDS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BorrowedFunds</Role>
      <ShortName>BORROWED FUNDS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - DEPOSITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/Deposits</Role>
      <ShortName>DEPOSITS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/CapitalRatiosAndShareholdersEquity</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - EARNINGS PER SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/EarningsPerShare</Role>
      <ShortName>EARNINGS PER SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DerivativeFinancialInstrumentsAndHedgingActivities</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/Leases</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - FAIR VALUE MEASUREMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurements</Role>
      <ShortName>FAIR VALUE MEASUREMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - NON-INTEREST INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/NonInterestIncome</Role>
      <ShortName>NON-INTEREST INCOME</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>218100 - Disclosure - SUBSEQUENT EVENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SubsequentEvents</Role>
      <ShortName>SUBSEQUENT EVENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - BASIS OF PRESENTATION (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BasisOfPresentationPolicies</Role>
      <ShortName>BASIS OF PRESENTATION (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2301302 - Disclosure - BASIS OF PRESENTATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BasisOfPresentationTables</Role>
      <ShortName>BASIS OF PRESENTATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/BasisOfPresentation</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2302301 - Disclosure - SECURITIES AVAILABLE FOR SALE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SecuritiesAvailableForSaleTables</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/SecuritiesAvailableForSale</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - LOANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansTables</Role>
      <ShortName>LOANS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/Loans</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - ALLOWANCE FOR LOAN LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/AllowanceForLoanLossesTables</Role>
      <ShortName>ALLOWANCE FOR LOAN LOSSES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/AllowanceForLoanLosses</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - BORROWED FUNDS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BorrowedFundsTables</Role>
      <ShortName>BORROWED FUNDS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/BorrowedFunds</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - DEPOSITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DepositsTables</Role>
      <ShortName>DEPOSITS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/Deposits</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/CapitalRatiosAndShareholdersEquityTables</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/CapitalRatiosAndShareholdersEquity</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - EARNINGS PER SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/EarningsPerShareTables</Role>
      <ShortName>EARNINGS PER SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/EarningsPerShare</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DerivativeFinancialInstrumentsAndHedgingActivitiesTables</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DerivativeFinancialInstrumentsAndHedgingActivities</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LeasesTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/Leases</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurementsTables</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/FairValueMeasurements</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - NON-INTEREST INCOME (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/NonInterestIncomeTables</Role>
      <ShortName>NON-INTEREST INCOME (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/NonInterestIncome</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2401403 - Disclosure - BASIS OF PRESENTATION - Recent Accounting Pronouncements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BasisOfPresentationRecentAccountingPronouncementsDetails</Role>
      <ShortName>BASIS OF PRESENTATION - Recent Accounting Pronouncements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2402402 - Disclosure - SECURITIES AVAILABLE FOR SALE - Summary of Securities Available for Sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SecuritiesAvailableForSaleSummaryOfSecuritiesAvailableForSaleDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Summary of Securities Available for Sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2402403 - Disclosure - SECURITIES AVAILABLE FOR SALE - Schedule of Maturity of Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SecuritiesAvailableForSaleScheduleOfMaturityOfSecuritiesDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Schedule of Maturity of Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2402404 - Disclosure - SECURITIES AVAILABLE FOR SALE - Summary of Securities with Unrealized Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SecuritiesAvailableForSaleSummaryOfSecuritiesWithUnrealizedLossesDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Summary of Securities with Unrealized Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2402405 - Disclosure - SECURITIES AVAILABLE FOR SALE - Securities Impairment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SecuritiesAvailableForSaleSecuritiesImpairmentDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Securities Impairment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2402406 - Disclosure - SECURITIES AVAILABLE FOR SALE - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SecuritiesAvailableForSaleNarrativeDetails</Role>
      <ShortName>SECURITIES AVAILABLE FOR SALE - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - LOANS - Summary of Total Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansSummaryOfTotalLoansDetails</Role>
      <ShortName>LOANS - Summary of Total Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - LOANS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansNarrativeDetails</Role>
      <ShortName>LOANS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2403404 - Disclosure - LOANS - Accretable Yield Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansAccretableYieldActivityDetails</Role>
      <ShortName>LOANS - Accretable Yield Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2403405 - Disclosure - LOANS - Summary of Past Due Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansSummaryOfPastDueLoansDetails</Role>
      <ShortName>LOANS - Summary of Past Due Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2403406 - Disclosure - LOANS - Summary Information Pertaining to Non-accrual Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansSummaryInformationPertainingToNonAccrualLoansDetails</Role>
      <ShortName>LOANS - Summary Information Pertaining to Non-accrual Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2403407 - Disclosure - LOANS - Loans Evaluated for Impairment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansLoansEvaluatedForImpairmentDetails</Role>
      <ShortName>LOANS - Loans Evaluated for Impairment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2403408 - Disclosure - LOANS - Summary of Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansSummaryOfImpairedLoansDetails</Role>
      <ShortName>LOANS - Summary of Impaired Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2403409 - Disclosure - LOANS - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansAverageRecordedInvestmentAndInterestIncomeRecognizedOnImpairedLoansDetails</Role>
      <ShortName>LOANS - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2403410 - Disclosure - LOANS - Recorded Investment and Number of Modifications (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LoansRecordedInvestmentAndNumberOfModificationsDetails</Role>
      <ShortName>LOANS - Recorded Investment and Number of Modifications (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - ALLOWANCE FOR LOAN LOSSES - Allowance Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/AllowanceForLoanLossesAllowanceActivityDetails</Role>
      <ShortName>ALLOWANCE FOR LOAN LOSSES - Allowance Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - ALLOWANCE FOR LOAN LOSSES - Loans by Credit Risk Rating (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/AllowanceForLoanLossesLoansByCreditRiskRatingDetails</Role>
      <ShortName>ALLOWANCE FOR LOAN LOSSES - Loans by Credit Risk Rating (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - BORROWED FUNDS - Summary of Borrowed Funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BorrowedFundsSummaryOfBorrowedFundsDetails</Role>
      <ShortName>BORROWED FUNDS - Summary of Borrowed Funds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2405403 - Disclosure - BORROWED FUNDS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BorrowedFundsNarrativeDetails</Role>
      <ShortName>BORROWED FUNDS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2405404 - Disclosure - BORROWED FUNDS - Summary of Maturities of FHLB (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/BorrowedFundsSummaryOfMaturitiesOfFhlbDetails</Role>
      <ShortName>BORROWED FUNDS - Summary of Maturities of FHLB (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - DEPOSITS - Schedule of Time Deposits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DepositsScheduleOfTimeDepositsDetails</Role>
      <ShortName>DEPOSITS - Schedule of Time Deposits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2406403 - Disclosure - DEPOSITS - Maturities by Year (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DepositsMaturitiesByYearDetails</Role>
      <ShortName>DEPOSITS - Maturities by Year (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2406404 - Disclosure - DEPOSITS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DepositsNarrativeDetails</Role>
      <ShortName>DEPOSITS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Actual and Required Capital Ratios (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/CapitalRatiosAndShareholdersEquityActualAndRequiredCapitalRatiosDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Actual and Required Capital Ratios (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of AOCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/CapitalRatiosAndShareholdersEquityComponentsOfAociDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of AOCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2407404 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of OCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/CapitalRatiosAndShareholdersEquityComponentsOfOciDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of OCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2407405 - Disclosure - CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Changes in AOCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/CapitalRatiosAndShareholdersEquityChangesInAociDetails</Role>
      <ShortName>CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Changes in AOCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - EARNINGS PER SHARE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/EarningsPerShareDetails</Role>
      <ShortName>EARNINGS PER SHARE (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/EarningsPerShareTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DerivativeFinancialInstrumentsAndHedgingActivitiesDerivativeAssetsAndLiabilitiesDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - LEASES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LeasesNarrativeDetails</Role>
      <ShortName>LEASES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/DerivativeFinancialInstrumentsAndHedgingActivitiesNarrativeDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/DerivativeFinancialInstrumentsAndHedgingActivitiesTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - LEASES - Operating Lease Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LeasesOperatingLeaseAssetsAndLiabilitiesDetails</Role>
      <ShortName>LEASES - Operating Lease Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - LEASES - Additional Lease Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LeasesAdditionalLeaseInformationDetails</Role>
      <ShortName>LEASES - Additional Lease Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2409405 - Disclosure - LEASES - Lease Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LeasesLeaseCostDetails</Role>
      <ShortName>LEASES - Lease Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2409406 - Disclosure - LEASES - Future Minimum Payments for Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/LeasesFutureMinimumPaymentsForLeasesDetails</Role>
      <ShortName>LEASES - Future Minimum Payments for Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - FAIR VALUE MEASUREMENTS - Measured on Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurementsMeasuredOnRecurringBasisDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Measured on Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - FAIR VALUE MEASUREMENTS - Changes in Level 3 (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurementsChangesInLevel3Details</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Changes in Level 3 (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2410404 - Disclosure - FAIR VALUE MEASUREMENTS - Unobservable Inputs Recurring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurementsUnobservableInputsRecurringDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Unobservable Inputs Recurring (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - FAIR VALUE MEASUREMENTS - Measured on Non-recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurementsMeasuredOnNonRecurringBasisDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Measured on Non-recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>2410406 - Disclosure - FAIR VALUE MEASUREMENTS - Unobservable Inputs Non-recurring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurementsUnobservableInputsNonRecurringDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Unobservable Inputs Non-recurring (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>2410407 - Disclosure - FAIR VALUE MEASUREMENTS - Fair Values and Carrying Amounts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/FairValueMeasurementsFairValuesAndCarryingAmountsDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Fair Values and Carrying Amounts (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - NON-INTEREST INCOME - Disaggregation of Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/NonInterestIncomeDisaggregationOfRevenueDetails</Role>
      <ShortName>NON-INTEREST INCOME - Disaggregation of Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - NON-INTEREST INCOME - Timing of Revenue Recognition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/NonInterestIncomeTimingOfRevenueRecognitionDetails</Role>
      <ShortName>NON-INTEREST INCOME - Timing of Revenue Recognition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - NON-INTEREST INCOME - Contract Balances from Contracts with Customers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/NonInterestIncomeContractBalancesFromContractsWithCustomersDetails</Role>
      <ShortName>NON-INTEREST INCOME - Contract Balances from Contracts with Customers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="bhb-20190630.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>248401 - Disclosure - SUBSEQUENT EVENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bhbt.com/role/SubsequentEventsDetails</Role>
      <ShortName>SUBSEQUENT EVENTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bhbt.com/role/SubsequentEvents</ParentRole>
      <Position>79</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-20190630.xml</File>
    <File>bhb-20190630.xsd</File>
    <File>bhb-20190630_cal.xml</File>
    <File>bhb-20190630_def.xml</File>
    <File>bhb-20190630_lab.xml</File>
    <File>bhb-20190630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/stpr/2018-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2018-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
