LOANS - Summary of Impaired Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Business Activities Loans
Recorded Investment
Total	$ 15,715	$ 9,647
Unpaid Principal Balance
Total	16,280	11,653
Related Allowance
With an allowance recorded:	796	459
Business Activities Loans \| Total Commercial Real Estate
Recorded Investment
Total	9,173	7,604
Unpaid Principal Balance
Total	9,410	9,598
Related Allowance
With an allowance recorded:	682	447
Business Activities Loans \| Total Commercial Real Estate \| Construction and land development
Recorded Investment
With no related allowance:	0	0
With an allowance recorded:	0	637
Unpaid Principal Balance
With no related allowance:	0	0
With an allowance recorded:	0	2,563
Related Allowance
With an allowance recorded:	0	59
Business Activities Loans \| Total Commercial Real Estate \| Other commercial real estate
Recorded Investment
With no related allowance:	7,102	5,896
With an allowance recorded:	2,071	1,071
Unpaid Principal Balance
With no related allowance:	7,270	5,903
With an allowance recorded:	2,140	1,132
Related Allowance
With an allowance recorded:	682	388
Business Activities Loans \| Commercial and industrial
Recorded Investment
Total	1,505	626
Unpaid Principal Balance
Total	1,522	625
Related Allowance
With an allowance recorded:	34	3
Business Activities Loans \| Commercial and industrial \| Other Commercial
Recorded Investment
With no related allowance:	726	218
With an allowance recorded:	779	408
Unpaid Principal Balance
With no related allowance:	736	217
With an allowance recorded:	786	408
Related Allowance
With an allowance recorded:	34	3
Business Activities Loans \| 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 \| 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 \| Residential Real Estate
Recorded Investment
Total	4,855	1,404
Unpaid Principal Balance
Total	4,885	1,417
Related Allowance
With an allowance recorded:	80	9
Business Activities Loans \| Residential Real Estate \| Residential mortgages
Recorded Investment
With no related allowance:	4,055	1,247
With an allowance recorded:	800	157
Unpaid Principal Balance
With no related allowance:	4,077	1,260
With an allowance recorded:	808	157
Related Allowance
With an allowance recorded:	80	9
Business Activities Loans \| Consumer
Recorded Investment
Total	182	13
Unpaid Principal Balance
Total	463	13
Related Allowance
With an allowance recorded:	0	0
Business Activities Loans \| Consumer \| Home equity
Recorded Investment
With no related allowance:	182	13
With an allowance recorded:	0	0
Unpaid Principal Balance
With no related allowance:	463	13
With an allowance recorded:	0	0
Related Allowance
With an allowance recorded:	0	0
Business Activities Loans \| 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	937	1,146
Unpaid Principal Balance
Total	1,060	1,370
Related Allowance
With an allowance recorded:	77	0
Acquired Loans \| Total Commercial Real Estate
Recorded Investment
Total	232	241
Unpaid Principal Balance
Total	342	352
Related Allowance
With an allowance recorded:	0	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:	232	241
With an allowance recorded:	0	0
Unpaid Principal Balance
With no related allowance:	342	352
With an allowance recorded:	0	0
Related Allowance
With an allowance recorded:	0	0
Acquired Loans \| Commercial and industrial
Recorded Investment
Total	422	571
Unpaid Principal Balance
Total	435	584
Related Allowance
With an allowance recorded:	77	0
Acquired Loans \| Commercial and industrial \| Other Commercial
Recorded Investment
With no related allowance:	49	571
With an allowance recorded:	373	0
Unpaid Principal Balance
With no related allowance:	49	584
With an allowance recorded:	386	0
Related Allowance
With an allowance recorded:	77	0
Acquired Loans \| 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 \| 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 \| Residential Real Estate
Recorded Investment
Total	283	271
Unpaid Principal Balance
Total	283	278
Related Allowance
With an allowance recorded:	0	0
Acquired Loans \| Residential Real Estate \| Residential mortgages
Recorded Investment
With no related allowance:	283	271
With an allowance recorded:	0	0
Unpaid Principal Balance
With no related allowance:	283	278
With an allowance recorded:	0	0
Related Allowance
With an allowance recorded:	0	0
Acquired Loans \| Consumer
Recorded Investment
Total	0	63
Unpaid Principal Balance
Total	0	156
Related Allowance
With an allowance recorded:	0	0
Acquired Loans \| Consumer \| Home equity
Recorded Investment
With no related allowance:	0	63
With an allowance recorded:	0	0
Unpaid Principal Balance
With no related allowance:	0	156
With an allowance recorded:	0	0
Related Allowance
With an allowance recorded:	0	0
Acquired Loans \| 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84173941&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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84173941&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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84173941&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: