Restrictions on Cash (Details 1) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Required minimum average reserve balance based on the amount of deposits held with the Federal Reserve Bank	$ 73.2	$ 153.4

The required minimum average cash reserve maintained with the Federal Reserve Bank based on the amount of deposits held with the Federal Reserve Bank.

No definition available.

Name:	boh_RequiredMinimumAverageCashReserveMaintainedWithFederalReserveBank
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant