Commitments, Contingencies and Guarantees - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020 USD ($) Activity	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) Activity
Commitments and Contingencies Disclosure [Line Items]
Notional amount outstanding	$ 0	$ 0
Open futures contract positions and average	$ 0	0
Net future activity | Activity	0		0
Gain (loss) from net futures activity		5,000
Average of contracts to purchase and to sell foreign currency	$ 21,000,000.0	18,400,000
Net gains on foreign exchange contracts	1,900,000	1,800,000	$ 2,100,000
ACL for off-balance sheet credit exposures	5,588,000	2,978,000
Provision for off-balance sheet credit exposures	2,610,000
Accrued Expenses and Taxes [Member]
Commitments and Contingencies Disclosure [Line Items]
ACL for off-balance sheet credit exposures	$ 5,600,000
Maximum [Member]
Commitments and Contingencies Disclosure [Line Items]
Standby letters of credit term	6 years
Standby letters of credit	$ 346,600,000	299,900,000
Minimum [Member]
Commitments and Contingencies Disclosure [Line Items]
Standby letters of credit term	3 months
Related Parties [Member]
Commitments and Contingencies Disclosure [Line Items]
Standby letters of credit	$ 3,800,000	$ 3,700,000