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Loans - Additional Information (Detail) - USD ($)
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Residential mortgage loan $ 36,700,000 $ 38,000,000.0    
Loans 1,345,887,000 1,305,473,000    
Allowance for loan losses 14,425,000 13,672,000   $ 7,228,000
Commercial and Industrial [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Loans 202,958,000 $ 189,246,000    
Allowance for loan losses 0      
Commercial and Industrial [Member] | PPP Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Loans $ 51,800,000   $ 36,200,000