Parent Company - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 1,040,944	$ 694,017	$ 1,003,637	$ 1,034,644
Other assets	603,463	490,573
Total assets	22,662,831	20,166,734	20,695,678
Liabilities and Stockholders' Equity
Retirement benefits payable	143,373	138,222
Other liabilities	347,621	343,241
Total liabilities	19,918,727	17,526,476
Stockholders' equity
Stockholders' equity	2,744,104	2,640,258	2,524,839	2,532,551
Total liabilities and stockholders' equity	22,662,831	20,166,734
Parent Company.
Assets
Cash and cash equivalents	18,066	24,455	$ 5,647	$ 14,337
Investment in FHB	2,726,497	2,617,949
Other assets	26,138	24,969
Total assets	2,770,701	2,667,373
Liabilities and Stockholders' Equity
Retirement benefits payable	580	553
Other liabilities	26,017	26,562
Total liabilities	26,597	27,115
Stockholders' equity
Total liabilities and stockholders' equity	$ 2,770,701	$ 2,667,373