Investment Securities - Other-Than-Temporary Impairment (Details) $ in Millions	1 Months Ended	12 Months Ended
Jan. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Investment Securities
Total OTTI write-downs included in earnings		$ 24.1
Number of securities intended to sell or sold \| security	48	48
Amortized cost of securities intended to sell		$ 898.2
Additional loss from sale of securities	$ 2.6

Represents the amortized cost basis of securities intended to sell.

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Represents the number of securities intended to sell or sold.

+ References

No definition available.

+ Details

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Namespace Prefix:	fhb_
Data Type:	xbrli:integerItemType
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Period Type:	duration

- References

No definition available.

+ Details

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- Definition

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 8B
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=SL6284393-111563

+ Details

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

- Definition

Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=109979856&loc=SL6284422-111562

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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