Derivative Financial Instruments - Amounts Recorded in Balance Sheets Related to Cumulative Basis Adjustments (Details) - Location, Statement of Financial Position, Balance [Axis]: fhb:FinancingReceivableAndNetInvestmentInLeaseExcludingAccruedInterestBeforeAllowanceForCreditLoss - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Amounts recorded in the balance Sheets
Carrying Amount of the Hedged Asset	$ 49,791	$ 52,491
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Asset	$ (8,334)	$ (7,509)

Derivative Financial Instruments - Amounts Recorded in Balance Sheets Related to Cumulative Basis Adjustments (Details) - Location, Statement of Financial Position, Balance [Axis]: fhb:FinancingReceivableAndNetInvestmentInLeaseExcludingAccruedInterestBeforeAllowanceForCreditLoss - USD ($)
$ in Thousands

Jun. 30, 2026

Dec. 31, 2025

Amounts recorded in the balance Sheets

Carrying Amount of the Hedged Asset

$ 49,791

$ 52,491

Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Asset

$ (8,334)

$ (7,509)