Organization and Summary of Significant Accounting Policies - Investment Securities (Details)	12 Months Ended
Dec. 31, 2021
Organization and Summary of Significant Accounting Policies
Investment securities comprised of collateralized loan obligations rated AA or better and obligations issued by local state and political subdivisions rated AA or better	2.00%

Percentage of securities comprised of collateralized loan obligations rated AA or better and obligations issued by local state and political subdivisions rated AA or better.

No definition available.

Name:	fhb_PercentageOfSecuritiesComprisedOfCollateralizedLoanObligationsRatedAaOrBetterAndObligationsIssuedByLocalStateAndPoliticalSubdivisionsRatedAaOrBetter
Namespace Prefix:	fhb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration