Allowance for Loan Losses - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Originated
Loans and Leases Receivable Disclosure [Line Items]
Interest income on non accrual loans	$ 896,000	$ 1,584,000	$ 1,067,000
Interest income on non accrual loans ,recognized	210,000	486,000	530,000
Impaired TDR Loans	7,285,000	10,253,000	12,517,000
PNCI
Loans and Leases Receivable Disclosure [Line Items]
Interest income on non accrual loans	305,000	1,122,000	73,000
Interest income on non accrual loans ,recognized	162,000	989,000	18,000
Impaired TDR Loans	726,000	615,000	1,352,000
Obligation Related To Troubled Debt Restructuring	$ 0	$ 0	$ 0