Organization and Basis of Presentation - Basis of Presentation (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2022	Sep. 30, 2022	Dec. 31, 2021
Capitalization
Investment securities comprised of collateralized loan obligations rated AA or better and obligations issued by local state and political subdivisions rated AA or better		4.00%	4.00%
Credit losses recognized on securities	$ 0	$ 0	$ 0
First Hawaiian, Inc. (FHI)
Capitalization
Outstanding common stock owned (as a percent)	100.00%	100.00%

Percentage of securities comprised of collateralized loan obligations rated AA or better and obligations issued by local state and political subdivisions rated AA or better.

No definition available.

+ Details

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- Definition

Amount of increase (decrease) in allowance for credit loss of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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- 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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- Details

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