BASIS OF PRESENTATION - Tax Cuts and Jobs Act (Details) $ in Millions	3 Months Ended
Dec. 31, 2017 USD ($)
Revenue from Contract with Customer [Abstract]
Remeasurement of net deferred tax asset resulting in additional income tax expense	$ 4.0

Amount of income tax expense (benefit) for remeasurement of deferred tax from change in tax rate pursuant to Tax Cuts and Jobs Act.

No definition available.

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