Income Taxes - Examinations (Details)	9 Months Ended
Sep. 30, 2018 item
Income Taxes
Number of examinations under way	0

The number of income tax examinations that an enterprise is currently subject to or that have not been completed.

No definition available.

Name:	fhb_IncomeTaxExaminationNumberOfExaminationsInProgress
Namespace Prefix:	fhb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration