Stock-Based Compensation - Employee Stock Purchase Plan (Details) - shares	1 Months Ended		12 Months Ended
	Jul. 31, 2020	Jan. 31, 2018	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
First Hawaiian Incorporated
Stock-based compensation
Total shares authorized			600,000
Shares available for future purchases			498,653
Employee Stock Purchase Plan
Stock-based compensation
Discount from the closing price on the exercise date (as a percent)	5.00%	5.00%
Holding period for common stock purchased by plan participants			2 years
Shares issued to employee participants			16,226	16,680	21,070