Represents the funding swap agreement contingent conversion rate.

No definition available.

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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

The estimated payment paid to the buyer as a result of the reduction in the conversion rate.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of shares of an investment sold during the period.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The number of shares received by the entity from issuer in a stock transaction.

+ References

No definition available.

+ Details

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Namespace Prefix:	fhb_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Cost to investors of each class of capital shares or other capital units.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04.16(b)(1))
-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

+ References

No definition available.

+ Details

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

- Definition

Balance held at close of period in number of shares.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
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-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611225-123010

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-Name Accounting Standards Codification
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-SubTopic 320
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-12.Column B)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611133-123010

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
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

- Details

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Data Type:	na
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- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
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Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
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- Details

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Investment Securities - Visa Class B Restricted Shares (Details) $ in Thousands	12 Months Ended		96 Months Ended
	Dec. 31, 2016 USD ($) shares	Dec. 31, 2008 USD ($) shares	Dec. 31, 2015 shares	Mar. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Jul. 31, 2018 USD ($)	Jun. 28, 2018	Dec. 31, 2017
Visa \| Class B restricted shares
Visa Class B Restricted Shares
Historical cost included in the balance sheets		$ 0
Net realized gain related to the sale of stock	$ 22,700
Number of shares sold \| shares	274,000		0
Shares held \| shares				120,000	120,000
Cost basis				$ 0	$ 0
Visa \| Class B restricted shares
Visa Class B Restricted Shares
Stock received in initial public offering (in shares) \| shares		394,000
Funding Swap (Visa Derivative) \| Class B restricted shares
Visa Class B Restricted Shares
Conversion rate							1.6298	1.6483
Funding Swap (Visa Derivative) \| Visa
Visa Class B Restricted Shares
Estimated liability that was subsequently paid to the buyer						$ 700