LOANS AND ALLOWANCE FOR CREDIT LOSSES - Allowance Activity (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Activity in the allowance for loan losses
Balance at beginning of period	$ 19,082	$ 15,353	$ 13,866
Charged-off loans	(898)	(2,168)	(1,153)
Recoveries on charged-off loans	608	272	323
Provision for credit losses	(1,302)	5,625	2,317
Balance at end of period	22,718	19,082	15,353
Allowance For Loan Losses
Individually evaluated for impairment			1,513
Collectively evaluated			13,840
impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	5,228
Balance at end of period		5,228
Total commercial real estate
Activity in the allowance for loan losses
Balance at beginning of period		7,815	6,984
Charged-off loans			(212)
Recoveries on charged-off loans			194
Provision for credit losses			849
Balance at end of period			7,815
Allowance For Loan Losses
Individually evaluated for impairment			1,243
Collectively evaluated			6,572
Total commercial and industrial
Activity in the allowance for loan losses
Balance at beginning of period		3,614	2,415
Charged-off loans			(359)
Recoveries on charged-off loans			65
Provision for credit losses			1,493
Balance at end of period			3,614
Allowance For Loan Losses
Individually evaluated for impairment			164
Collectively evaluated			3,450
Total residential real estate
Activity in the allowance for loan losses
Balance at beginning of period		3,545	4,059
Charged-off loans			(349)
Recoveries on charged-off loans			55
Provision for credit losses			(220)
Balance at end of period			3,545
Allowance For Loan Losses
Individually evaluated for impairment			106
Collectively evaluated			3,439
Total consumer
Activity in the allowance for loan losses
Balance at beginning of period		379	408
Charged-off loans			(233)
Recoveries on charged-off loans			9
Provision for credit losses			195
Balance at end of period			379
Allowance For Loan Losses
Collectively evaluated			379
Construction and land development \| Total commercial loans
Activity in the allowance for loan losses
Balance at beginning of period	824	317
Recoveries on charged-off loans	18
Provision for credit losses	73	507
Balance at end of period	2,111	824	317
Construction and land development \| Total commercial loans \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	1,196
Balance at end of period		1,196
Commercial real estate owner occupied \| Total commercial real estate
Activity in the allowance for loan losses
Balance at beginning of period	1,783	2,368
Charged-off loans	(403)
Recoveries on charged-off loans	290
Provision for credit losses	373	(585)
Balance at end of period	2,751	1,783	2,368
Commercial real estate owner occupied \| Total commercial real estate \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	708
Balance at end of period		708
Commercial real estate non-owner occupied \| Total commercial real estate
Activity in the allowance for loan losses
Balance at beginning of period	7,864	4,695
Charged-off loans		(1,137)
Recoveries on charged-off loans	4	173
Provision for credit losses	(210)	4,133
Balance at end of period	5,650	7,864	4,695
Commercial real estate non-owner occupied \| Total commercial real estate \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	(2,008)
Balance at end of period		(2,008)
Tax exempt
Activity in the allowance for loan losses
Balance at beginning of period	58	67
Provision for credit losses	(12)	(9)
Balance at end of period	86	58	67
Tax exempt \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	40
Balance at end of period		40
Commercial and industrial \| Total commercial and industrial
Activity in the allowance for loan losses
Balance at beginning of period	3,137	3,262
Charged-off loans	(59)	(593)
Recoveries on charged-off loans	77	30
Provision for credit losses	(782)	438
Balance at end of period	5,369	3,137	3,262
Commercial and industrial \| Total commercial and industrial \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	2,996
Balance at end of period		2,996
Residential mortgages \| Total residential real estate
Activity in the allowance for loan losses
Balance at beginning of period	5,010	4,213
Charged-off loans	(77)	(54)
Recoveries on charged-off loans	159	13
Provision for credit losses	(962)	838
Balance at end of period	5,862	5,010	4,213
Residential mortgages \| Total residential real estate \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	1,732
Balance at end of period		1,732
Home equity
Activity in the allowance for loan losses
Balance at beginning of period	285	320
Charged-off loans	(154)
Recoveries on charged-off loans	51
Provision for credit losses	29	(35)
Balance at end of period	814	285	320
Home equity \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	603
Balance at end of period		603
Other consumer \| Total consumer
Activity in the allowance for loan losses
Balance at beginning of period	121	111
Charged-off loans	(205)	(384)
Recoveries on charged-off loans	9	56
Provision for credit losses	189	338
Balance at end of period	75	121	111
Other consumer \| Total consumer \| impact of ASC 326
Activity in the allowance for loan losses
Balance at beginning of period	(39)
Balance at end of period		(39)
Unfunded Loan Commitment
Activity in the allowance for loan losses
Balance at beginning of period	359	314	304
Provision for credit losses	177	45	10
Balance at end of period	2,152	$ 359	$ 314
Unfunded Loan Commitment \| impact of ASC 326
Activity in the allowance for loan losses
Balance at end of period	$ 1,616

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

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

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=122038336&loc=d3e74567-122707

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

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

- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_ProvisionForLoanAndLeaseLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember
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_FinancingReceivablePortfolioSegmentAxis=bhb_CommercialAndIndustrialLoansPortfolioSegmentMember
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_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
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_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bhb_CommercialRealEstateNonOwnerOccupiedMember
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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bhb_CommercialAndIndustrialMember
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_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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_UnfundedLoanCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: