Reportable Operating Segments - Business Segments (Details)	3 Months Ended
Mar. 31, 2020 location segment
Reportable operating segments
Number of business segments \| segment	3
Retail Banking
Reportable operating segments
Number of Branches \| location	58

Represents the number of branches that offers a comprehensive suite of banking services to consumer and commercial customers including loans, deposit products, wealth management, insurance, trust, retirement planning, credit card and merchant processing services.

No definition available.

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