Organization and Basis of Presentation - Loans and Leases (Details) $ in Millions	Jun. 30, 2020 USD ($)
Organization and Basis of Presentation.
Accrued interest receivable related to loans and leases recorded separately	$ 48.7

Accrued interest receivable related to loans and leases recorded separately from the amortized cost basis of loans and leases on the balance sheet.

No definition available.

Name:	fhb_AccruedInterestReceivableRelatedToLoansAndLeases
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant