Organization and Basis of Presentation (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)
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%	100.00%

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