Represents capital distributions to the entity's stockholder.

No definition available.

Name:	fhb_CapitalDistributions
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of current and deferred federal income tax expense (benefit) attributable to distribution taxes.

+ References

No definition available.

+ Details

Name:	fhb_DistributionTaxesFederalIncomeTaxExpenseBenefit
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The reported amount of obligation for state and local distribution taxes of a prior period tax return.

+ References

No definition available.

+ Details

Name:	fhb_DistributionTaxesStateAndLocalObligationReportedAmountPriorPeriodTaxReturn
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The estimated amount of indemnification liability recognized for income tax contingencies.

+ References

No definition available.

+ Details

Name:	fhb_IncomeTaxContingenciesIndemnificationLiability
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The estimated amount of indemnification receivable recognized for income tax contingencies attributable to transactions prior to change in reporting entity.

+ References

No definition available.

+ Details

Name:	fhb_IncomeTaxContingenciesIndemnificationReceivableTransactionsPriorToChangeInReportingEntity
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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:	fhb_IncomeTaxLineItems
Namespace Prefix:	fhb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes attributable to transactions prior to change in reporting entity.

+ References

No definition available.

+ Details

Name:	fhb_IncomeTaxesReceivableCurrentTransactionsPriorToChangeInReportingEntity
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The net amount of increase (decrease) in the estimated amount of indemnification liability (receivable) recognized for income tax contingencies attributable to transactions prior to change in reporting entity and unrecognized tax benefits attributable to change in reporting entity, including transactions prior to change in reporting entity and related reorganization transactions.

+ References

No definition available.

+ Details

Name:	fhb_IncreaseDecreaseIncomeTaxContingenciesIndemnificationLiabilityReceivableAndUnrecognizedTaxBenefitsChangeInReportingEntityNet
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net amount of increase (decrease) in the estimated amount of indemnification liability (receivable) recognized for income tax contingencies attributable to transactions prior to change in reporting entity and unrecognized tax expense attributable to change in reporting entity, including transactions prior to change in reporting entity and related reorganization transactions.

+ References

No definition available.

+ Details

Name:	fhb_IncreaseDecreaseIncomeTaxContingenciesIndemnificationLiabilityReceivableAndUnrecognizedTaxExpenseChangeInReportingEntityNet
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of unrecognized tax benefits attributable to change in reporting entity, including related reorganization transactions.

+ References

No definition available.

+ Details

Name:	fhb_UnrecognizedTaxBenefitsChangeInReportingEntity
Namespace Prefix:	fhb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(a)(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_IncomeTaxesReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable for statutory income, sales, use, payroll, excise, real, property and other taxes. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_TaxesPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=fhb_ReorganizationTransactionsApril2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income Taxes - Reorganization Transactions - (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 01, 2016	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income taxes
Current tax receivables related to transactions prior to Reorganization Transactions		$ 130.5
Unrecognized tax positions		159.0	$ 160.6
Indemnification receivable		28.5	30.1
Total state and local distribution taxes reported		92.1
Net adjustments to pre-reorganization indemnification receivables or payables and unrecognized tax benefits		2.1	$ 2.5	$ 0.0
Provision for income taxes and noninterest expense		3.8
Reorganization Transactions on April 1, 2016
Income taxes
Current tax receivables recorded	$ 72.8
Unrecognized tax positions	116.6
Indemnification payable	28.6
Certain tax related liabilities incurred	95.4
Expected federal tax benefit on distribution taxes	$ 33.4
Capital distributions		$ 2.1