FAIR VALUE MEASUREMENTS - Unobservable Inputs Non-recurring (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Quantitative information about the significant unobservable inputs within Level 3
Other real estate owned	$ 122,000	$ 90,000
Non-recurring \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Total	15,073,000	6,804,000
Non-recurring \| Fair value of collateral - appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans	8,586,000	3,268,000
Other real estate owned	122,000	90,000
Non-recurring \| Discounted cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans	2,207,000	3,441,000
Capitalized servicing rights	4,158,000	5,000
Non-recurring \| Impaired loans \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans	$ 10,793,000	$ 6,709,000
Non-recurring \| Impaired loans \| Minimum \| Fair value of collateral - appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Loss severity	15.70%	0.00%
Appraised value	$ 100,000	$ 0
Non-recurring \| Impaired loans \| Minimum \| Discounted cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Discount rate	2.63%	3.25%
Cash flows	$ 6,000	$ 6,000
Non-recurring \| Impaired loans \| Maximum \| Fair value of collateral - appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Loss severity	45.28%	51.00%
Appraised value	$ 7,545,000	$ 1,732,000
Non-recurring \| Impaired loans \| Maximum \| Discounted cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Discount rate	9.50%	18.25%
Cash flows	$ 320,000	$ 861,000
Non-recurring \| Capitalized servicing rights \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Capitalized servicing rights	$ 4,158,000	$ 5,000
Non-recurring \| Capitalized servicing rights \| Discounted cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Discount rate	10.10%	7.55%
Constant prepayment rate (CPR)	10.97%	17.09%
Non-recurring \| Other real estate owned \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Other real estate owned	$ 122,000	$ 90,000
Non-recurring \| Other real estate owned \| Fair value of collateral - appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Appraised value	$ 122	$ 120

Represents the appraised value used as an input to measure fair value.

No definition available.

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

- Definition

Fair Value Inputs, Cash Flow

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of impaired loans assets reported on the balance sheet at period end measured at fair value by the entity.

+ References

No definition available.

+ Details

Name:	bhb_ImpairedLoansFairValueDisclosure
Namespace Prefix:	bhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
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

No definition available.

+ Details

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

- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsLossSeverity
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsPrepaymentRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04(c)(Schedule III))
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5162-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4437-111522

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 970
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28)
-URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024

+ Details

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

- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

+ Details

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

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
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_ValuationTechniqueAxis=bhb_FairValueOfCollateralValuationTechniqueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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