Other Assets - Quantitative Assumptions Used for MSRs (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Minimum
Quantitative assumptions used in determining lower of cost or fair value of MSRs
Conditional prepayment rate (as a percent)	7.86%	8.53%
Life (of the MSR)	3 years 5 months 5 days	3 years 3 months 15 days
Weighted-average coupon rate (as a percent)	3.97%	3.97%
Discount rate (as a percent)	10.00%	10.50%
Maximum
Quantitative assumptions used in determining lower of cost or fair value of MSRs
Conditional prepayment rate (as a percent)	19.26%	19.63%
Life (of the MSR)	7 years 8 months 5 days	7 years 1 month 24 days
Weighted-average coupon rate (as a percent)	6.70%	6.79%
Discount rate (as a percent)	10.02%	10.52%
Weighted Average
Quantitative assumptions used in determining lower of cost or fair value of MSRs
Conditional prepayment rate (as a percent)	8.31%	9.04%
Life (of the MSR)	7 years 2 months 9 days	6 years 9 months 4 days
Weighted-average coupon rate (as a percent)	4.02%	4.04%
Discount rate (as a percent)	10.00%	10.50%

Weighted average coupon rate used to estimate the fair value of servicing assets and servicing liabilities.

No definition available.

Name:	fhb_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueWeightedAverageCouponRate
Namespace Prefix:	fhb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122596-111746

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

+ References

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValuePrepaymentSpeed
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average life of financial assets and financial liabilities, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueWeightedAverageLife1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ServicingAssetsAtFairValueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: