v3.26.1
Noninterest Income and Noninterest Expense - Net periodic benefit cost (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension Benefits        
Components of net periodic benefit cost        
Interest cost $ 1,713 $ 1,879 $ 3,425 $ 3,759
Interest cost component Other Other Other Other
Expected return on plan assets $ (831) $ (876) $ (1,662) $ (1,752)
Expected return on plan assets, component Other Other Other Other
Recognized net actuarial loss (gain) $ 278 $ 383 $ 556 $ 766
Recognized net actuarial loss (gain), component Other Other   Other
Total net periodic benefit cost $ 1,160 $ 1,386 2,319 $ 2,773
Other Benefits        
Components of net periodic benefit cost        
Interest cost $ 225 $ 225 $ 449 $ 450
Interest cost component Other Other Other Other
Recognized net actuarial loss (gain) $ (218) $ (301) $ (436) $ (602)
Recognized net actuarial loss (gain), component Other Other Other Other
Total net periodic benefit cost $ 210 $ 93 $ 419 $ 186
Other Benefits | Location, Statement of Income, Balance [Axis]: fhb:SalariesAndEmployeeBenefitsMember        
Components of net periodic benefit cost        
Service cost $ 203 $ 169 $ 406 $ 338