Transactions with Affiliates and Related Parties - Summary of Transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Related party transactions
Other liabilities	$ 0	$ 0	$ 0
Off-balance sheet commitments with affiliates to purchase and sell foreign currencies	0	0	$ 0
Related parties associated with its branch premises
Related party transactions
Cash and due from banks		55,454,000
Other assets		19,358,000
Noninterest-bearing demand deposits		(346,000)
Noninterest income from affiliates	382,000	5,677,000
Noninterest expense to affiliates	(4,000)	(59,000)
BancWest Corporation (BWC) | Expense reimbursements
Related party transactions
Payments received from BWC	$ 7,200,000	$ 14,600,000