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Organization and Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2025	Sep. 30, 2025
Capitalization
Amount of income tax expense (benefit)	$ 5.1	$ 5.1
First Hawaiian, Inc. (FHI)
Capitalization
Outstanding common stock owned (as a percent)			100.00%

X

- Definition

Amount of income tax expense (benefit) due to remeasurement adjustment of change in tax legislation.

+ References

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+ Details

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X

- Definition

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

+ References

No definition available.

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X

- 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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X

- Details

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