Parent Company - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 694,017	$ 1,003,637	$ 1,034,644	$ 1,052,058
Other assets	490,573	446,404
Total assets	20,166,734	20,695,678	20,549,461
Liabilities and Stockholders' Equity
Retirement benefits payable	138,222	127,909
Other liabilities	343,241	292,836
Total liabilities	17,526,476	18,170,839
Stockholders' equity
Stockholders' equity	2,640,258	2,524,839	2,532,551	2,476,485
Total liabilities and stockholders' equity	20,166,734	20,695,678
Parent Company
Assets
Cash and cash equivalents	24,455	5,647	$ 14,337	$ 5,994
Investment in FHB	2,617,949	2,521,347
Other assets	24,969	19,358
Total assets	2,667,373	2,546,352
Liabilities and Stockholders' Equity
Retirement benefits payable	553	509
Other liabilities	26,562	21,004
Total liabilities	27,115	21,513
Stockholders' equity
Stockholders' equity	2,640,258	2,524,839
Total liabilities and stockholders' equity	$ 2,667,373	$ 2,546,352