Regulatory Capital Requirements (Details) $ / shares in Units, $ in Thousands	1 Months Ended
	Apr. 30, 2025 $ / shares	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Common equity tier 1 capital to risk-weighted assets
Amount		$ 2,083,979	$ 2,083,938
Ratio (as a percent)		0.1293	0.128
Minimum Capital Ratio (as a percent)		0.045	0.045
Well-Capitalized Ratio (as a percent)		0.065	0.065
Tier 1 capital to risk-weighted assets
Amount		$ 2,083,979	$ 2,083,938
Ratio (as a percent)		0.1293	0.128
Minimum Capital Ratio (as a percent)		0.06	0.06
Well-Capitalized Ratio (percent)		0.08	0.08
Total capital to risk-weighted assets
Amount		$ 2,283,938	$ 2,277,178
Ratio (as a percent)		0.1417	0.1399
Minimum Capital Ratio (as a percent)		0.08	0.08
Well-Capitalized Ratio (as a percent)		0.10	0.10
Tier 1 capital to average assets (leverage ratio)
Amount		$ 2,083,979	$ 2,083,938
Ratio		0.0901	0.0914
Minimum Capital Ratio (as a percent)		0.04	0.04
Well-Capitalized Ratio (percent)		0.05	0.05
Common Stock | 2025 Q2 Dividend | Subsequent event
Tier 1 capital to average assets (leverage ratio)
Dividend declared date	2025-04
Quarterly cash dividend (dollars per share) | $ / shares	$ 0.26
Dividend paid date	May 30, 2025
Dividend record date	May 19, 2025
First Hawaiian Bank (FHB)
Common equity tier 1 capital to risk-weighted assets
Amount		$ 2,074,202	$ 2,070,403
Ratio (as a percent)		0.1287	0.1271
Tier 1 capital to risk-weighted assets
Amount		$ 2,074,202	$ 2,070,403
Ratio (as a percent)		0.1287	0.1271
Total capital to risk-weighted assets
Amount		$ 2,274,161	$ 2,263,643
Ratio (as a percent)		0.1411	0.139
Tier 1 capital to average assets (leverage ratio)
Amount		$ 2,074,202	$ 2,070,403
Ratio		0.0896	0.0908