Allowance for Credit Losses - Amortized Cost Basis of Loans and Leases on Nonaccrual Status (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Jan. 01, 2020
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans and Leases With No Allowance for Credit Losses	$ 3,156
Nonaccrual Loans and Leases	9,082	$ 5,468
Interest income on nonaccrual loans	200
Accrued interest receivables written off, Interest income reversed	1,400
Commercial and Industrial
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans and Leases	518	32
Commercial real estate
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans and Leases	80	30
Construction
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans and Leases With No Allowance for Credit Losses	1,840
Nonaccrual Loans and Leases	2,043
Residential
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans and Leases With No Allowance for Credit Losses	1,316
Nonaccrual Loans and Leases	$ 6,441	$ 5,406

Represents the interest receivable written off by reversing interest income.

No definition available.

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

- Definition

Amount of financing receivable on nonaccrual status with no allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447

+ Details

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Namespace Prefix:	us-gaap_
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

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

- Definition

Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447

+ Details

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

- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

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Balance Type:	credit
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- Details

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- Details

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- Details

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