FAIR VALUE MEASUREMENTS - Unobservable Inputs Recurring (Details)	9 Months Ended	12 Months Ended
Sep. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
FAIR VALUE MEASUREMENTS
Derivative asset (liability), fair value	$ 2,119,000	$ 2,122,000
Discount Cash Flows
FAIR VALUE MEASUREMENTS
Discount Rate		7.39%
Recurring \| Level 3
FAIR VALUE MEASUREMENTS
Total	1,689,000	$ 2,287,000
Recurring \| Level 3 \| Forward Commitments \| Quoted prices for similar loans in active markets
FAIR VALUE MEASUREMENTS
Derivative asset (liability), fair value	$ 394,000	$ (14,000)
Recurring \| Level 3 \| Forward Commitments \| Quoted prices for similar loans in active markets \| Minimum
FAIR VALUE MEASUREMENTS
Derivative asset (liability) net, measurement input	96,500	100,700
Recurring \| Level 3 \| Forward Commitments \| Quoted prices for similar loans in active markets \| Maximum
FAIR VALUE MEASUREMENTS
Derivative asset (liability) net, measurement input	101,400	103,400
Recurring \| Level 3 \| Corporate bonds \| Discount Cash Flows
FAIR VALUE MEASUREMENTS
Derivative asset (liability), fair value	$ 1,329,000	$ 2,203,000
Discount Rate	7.39%
Loss Severity	0.83%	0.65%
Recurring \| Level 3 \| Corporate bonds \| Discount Cash Flows \| Minimum
FAIR VALUE MEASUREMENTS
Cash Flows	$ 0	$ 0
Recurring \| Level 3 \| Corporate bonds \| Discount Cash Flows \| Maximum
FAIR VALUE MEASUREMENTS
Cash Flows	1,329,000	2,203,000
Recurring \| Level 3 \| Interest Rate Lock Commitment \| Pull-through Rate Analysis
FAIR VALUE MEASUREMENTS
Derivative asset (liability), fair value	$ (34,000)	$ 98,000
Closing Ratio	90.00%	96.00%
Recurring \| Level 3 \| Interest Rate Lock Commitment \| Pricing Model
FAIR VALUE MEASUREMENTS
Origination Costs, per loan	$ 1,700	$ 1,700
Recurring \| Level 3 \| Interest Rate Lock Commitment \| Discount Cash Flows
FAIR VALUE MEASUREMENTS
Derivative asset (liability) net, measurement input	0.01	0.01

Fair Value Inputs, Cash Flow

No definition available.

Name:	bhb_FairValueInputsCashFlow
Namespace Prefix:	bhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the closing ratio used as an input to measure fair value.

+ References

No definition available.

+ Details

Name:	bhb_FairValueInputsClosingRatio
Namespace Prefix:	bhb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value inputs, discount rate.

+ References

No definition available.

+ Details

Name:	bhb_FairValueInputsDiscountRate
Namespace Prefix:	bhb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value inputs, loss severity.

+ References

No definition available.

+ Details

Name:	bhb_FairValueInputsLossSeverity
Namespace Prefix:	bhb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair Value Inputs, Origination Cost Per Loan

+ References

No definition available.

+ Details

Name:	bhb_FairValueInputsOriginationCostPerLoan
Namespace Prefix:	bhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Value of input used to measure net derivative asset (liability).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_DerivativeAssetLiabilityNetMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-8

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-2

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 43
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479303/805-10-55-43

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 103
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-103

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

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

- Definition

Fair value of asset after deduction of liability.

+ References

+ Details

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

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_ValuationTechniqueDiscountedCashFlowMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ForwardContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_ValuationTechniqueConsensusPricingModelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_InterestRateLockCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=bhb_PullThroughRateAnalysisValuationTechniqueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_ValuationTechniqueMatrixPricingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: