LOANS - Summary of Impaired Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Business Activities Loans
Recorded Investment
Total	$ 12,738	$ 13,855
Unpaid Principal Balance
Total	13,188	14,124
Related Allowance
With an allowance recorded	1,297	611
Business Activities Loans \| Total commercial real estate
Recorded Investment
Total	8,759	9,835
Unpaid Principal Balance
Total	8,938	9,962
Related Allowance
With an allowance recorded	990	422
Business Activities Loans \| Total commercial real estate \| Construction and land development
Recorded Investment
With no related allowance	0	0
With an allowance recorded	1	1
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	1	1
Related Allowance
With an allowance recorded	1	1
Business Activities Loans \| Total commercial real estate \| Other commercial real estate
Recorded Investment
With no related allowance	5,634	8,209
With an allowance recorded	3,124	1,625
Unpaid Principal Balance
With no related allowance	5,675	8,301
With an allowance recorded	3,262	1,660
Related Allowance
With an allowance recorded	989	421
Business Activities Loans \| Total commercial and industrial
Recorded Investment
Total	1,323	1,445
Unpaid Principal Balance
Total	1,407	1,524
Related Allowance
With an allowance recorded	240	78
Business Activities Loans \| Total commercial and industrial \| Commercial
Recorded Investment
With no related allowance	657	649
With an allowance recorded	666	796
Unpaid Principal Balance
With no related allowance	713	669
With an allowance recorded	694	855
Related Allowance
With an allowance recorded	240	78
Business Activities Loans \| Total commercial and industrial \| Agricultural
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Business Activities Loans \| Total commercial and industrial \| Tax exempt
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Business Activities Loans \| Total residential real estate
Recorded Investment
Total	2,643	2,562
Unpaid Principal Balance
Total	2,830	2,625
Related Allowance
With an allowance recorded	66	111
Business Activities Loans \| Total residential real estate \| Residential mortgages
Recorded Investment
With no related allowance	2,082	1,671
With an allowance recorded	561	891
Unpaid Principal Balance
With no related allowance	2,236	1,709
With an allowance recorded	594	916
Related Allowance
With an allowance recorded	66	111
Business Activities Loans \| Total consumer
Recorded Investment
Total	13	13
Unpaid Principal Balance
Total	13	13
Related Allowance
With an allowance recorded	1	0
Business Activities Loans \| Total consumer \| Home equity
Recorded Investment
With no related allowance	0	0
With an allowance recorded	13	13
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	13	13
Related Allowance
With an allowance recorded	1	0
Business Activities Loans \| Total consumer \| Other consumer
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Acquired Loans
Recorded Investment
Total	1,644	1,358
Unpaid Principal Balance
Total	1,994	1,600
Related Allowance
With an allowance recorded	44	41
Acquired Loans \| Total commercial real estate
Recorded Investment
Total	257	188
Unpaid Principal Balance
Total	258	187
Related Allowance
With an allowance recorded	12	0
Acquired Loans \| Total commercial real estate \| Construction and land development
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Acquired Loans \| Total commercial real estate \| Other commercial real estate
Recorded Investment
With no related allowance	90	188
With an allowance recorded	167	0
Unpaid Principal Balance
With no related allowance	90	187
With an allowance recorded	168	0
Related Allowance
With an allowance recorded	12	0
Acquired Loans \| Total commercial and industrial
Recorded Investment
Total	414	426
Unpaid Principal Balance
Total	508	510
Related Allowance
With an allowance recorded	0	0
Acquired Loans \| Total commercial and industrial \| Commercial
Recorded Investment
With no related allowance	414	426
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	508	510
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Acquired Loans \| Total commercial and industrial \| Agricultural
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Acquired Loans \| Total commercial and industrial \| Tax exempt
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Acquired Loans \| Total residential real estate
Recorded Investment
Total	973	744
Unpaid Principal Balance
Total	1,228	903
Related Allowance
With an allowance recorded	32	41
Acquired Loans \| Total residential real estate \| Residential mortgages
Recorded Investment
With no related allowance	616	375
With an allowance recorded	357	369
Unpaid Principal Balance
With no related allowance	852	524
With an allowance recorded	376	379
Related Allowance
With an allowance recorded	32	41
Acquired Loans \| Total consumer
Recorded Investment
Total	0	0
Unpaid Principal Balance
Total	0	0
Related Allowance
With an allowance recorded	0	0
Acquired Loans \| Total consumer \| Home equity
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	0	0
Acquired Loans \| Total consumer \| Other consumer
Recorded Investment
With no related allowance	0	0
With an allowance recorded	0	0
Unpaid Principal Balance
With no related allowance	0	0
With an allowance recorded	0	0
Related Allowance
With an allowance recorded	$ 0	$ 0

No definition available.

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossAdditionalInformationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRelatedAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=bhb_LoansFromBusinessActivitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bhb_OtherCommercialRealEstateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=bhb_CommercialandIndustrialLoansPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bhb_OtherCommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bhb_AgricultureAndOtherLoansToFarmersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bhb_TaxExemptLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bhb_OtherConsumerLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=bhb_LoansAcquiredFromBusinessCombinationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: