Organization and Summary of Significant Accounting Policies - Basis of Presentation (Details) - location	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
First Hawaiian Bank
Capitalization
Outstanding common stock owned (as a percent)	100.00%	100.00%
First Hawaiian Bank
Capitalization
Number of banking locations	60

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