Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Notional Amount Of Performance Standby Letters Of Credit	$ 245,000
Notional Amount Of Commercial Letters Of Credit	0
Notional Amount Of Financial Standby Letters Of Credit	641,000
Financial instrument of credit risk	100,000	$ 100,000
Unfunded commitment liability	3,400,000	$ 4,500,000
Minimum [Member]
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	0
Maximum [Member]
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	$ 1,000,000