Commitments and Letters of Credit - Additional Information (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Notional amount of financial standby letters of credit	$ 2,600,000
Notional amount of performance standby letters of credit	300,000
Notional amount of commercial letters of credit	0
Financial instrument of credit risk	104,000	$ 138,000
Unused commitments and letters of credit [Member]
Loss Contingencies [Line Items]
Commitment liability	$ 7,400,000	$ 4,500,000