ALLOWANCE FOR LOAN LOSSES - Narrative (Details)	Jun. 30, 2018 USD ($)
Receivables [Abstract]
Specific reserve for loans individually evaluated, loan relationships with an aggregate balance (in excess)	$ 150,000

Allowance for Loan and Lease Loss, Minimum Aggregate Balance, Individually Evaluated for Specific Reserve

No definition available.

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