Regulatory Capital Requirements (Details) $ in Thousands	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Common equity tier 1 capital to risk-weighted assets
Amount	$ 1,863,915	$ 1,783,113
Ratio (as a percent)	0.1179	0.1224
Minimum Capital Ratio (as a percent)	0.0450	0.0450
Well-Capitalized Ratio (as a percent)	0.0650	0.0650
Tier 1 capital to risk-weighted assets
Amount	$ 1,863,915	$ 1,783,113
Ratio (as a percent)	0.1179	0.1224
Minimum Capital Ratio (as a percent)	0.0600	0.0600
Well-Capitalized Ratio (percent)	0.0800	0.0800
Total capital to risk-weighted assets
Amount	$ 2,042,219	$ 1,965,280
Ratio (as a percent)	0.1292	0.1349
Minimum Capital Ratio (as a percent)	0.0800	0.0800
Well-Capitalized Ratio (as a percent)	0.1000	0.1000
Tier 1 capital to average assets (leverage ratio)
Amount	$ 1,863,915	$ 1,783,113
Ratio	0.0778	0.0724
Minimum Capital Ratio (as a percent)	0.0400	0.0400
Well-Capitalized Ratio (percent)	0.0500	0.0500
First Hawaiian Bank (FHB)
Common equity tier 1 capital to risk-weighted assets
Amount	$ 1,846,735	$ 1,769,214
Ratio (as a percent)	0.1168	0.1214
Tier 1 capital to risk-weighted assets
Amount	$ 1,846,735	$ 1,769,214
Ratio (as a percent)	0.1168	0.1214
Total capital to risk-weighted assets
Amount	$ 2,025,039	$ 1,951,377
Ratio (as a percent)	0.1281	0.1340
Tier 1 capital to average assets (leverage ratio)
Amount	$ 1,846,735	$ 1,769,214
Ratio	0.0771	0.0718