Annual report pursuant to Section 13 and 15(d)

Loans - Additional Information (Details)

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Loans - Additional Information (Details) - USD ($)
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]      
Pledged loans, collateral for FHLB advances $ 993,400,000 $ 927,300,000  
Pledged loans, collateral under PPPLF   149,800,000  
Amount outstanding [1] 2,322,101,000 2,388,532,000  
Unfunded commitments to related parties 554,006,000 312,683,000  
Executive Officers and Directors      
Accounts Notes And Loans Receivable [Line Items]      
Unfunded commitments to related parties 1,200,000 861,000  
Consumer Mortgage Loans      
Accounts Notes And Loans Receivable [Line Items]      
Recorded mortgage loans in process of foreclosure 0 0  
SBA Loans      
Accounts Notes And Loans Receivable [Line Items]      
Paycheck protection program loans under CARES Act $ 43,900,000    
PPP loan interest rate 1.00%    
Weighted average life of debt 3 years 3 months 18 days    
Interest rate 0.35%    
Unpaid principal balances of loans serviced $ 154,300,000 193,300,000  
Loan expenses 1,200,000 1,200,000 $ 929,000
SBA Loans | Third Party      
Accounts Notes And Loans Receivable [Line Items]      
Servicing loans sold 10,100,000 21,100,000 47,800,000
Realized gains on servicing loans sold 967,000 1,800,000 $ 4,000,000.0
SBA Loans | Loan Forgiveness and Normal Amortization      
Accounts Notes And Loans Receivable [Line Items]      
Origination fees net of costs 8,000,000.0    
Remaining origination fees net of costs $ 979,000    
SBA Loans | Minimum      
Accounts Notes And Loans Receivable [Line Items]      
Paycheck protection program loans contractual term 2 years    
SBA Loans | Maximum      
Accounts Notes And Loans Receivable [Line Items]      
Paycheck protection program loans contractual term 5 years    
SBA Loans | Commercial and Industrial Loans      
Accounts Notes And Loans Receivable [Line Items]      
Paycheck protection program loans under CARES Act   277,800,000  
SBA Loans | Commercial and Industrial Loans | Loan Forgiveness and Normal Amortization      
Accounts Notes And Loans Receivable [Line Items]      
Origination fees net of costs   7,100,000  
Federal Reserve Bank Of Boston Special Purpose Vehicle | Main Street Lending Program      
Accounts Notes And Loans Receivable [Line Items]      
Servicing loans sold $ 10,500,000 400,300,000  
Realized gains on servicing loans sold 99,000 $ 3,600,000  
Unpaid principal balances of loans serviced $ 333,100,000    
Percentage of loan balance purchased 95.00%    
[1] Balance includes $(8.1) and $(8.2) million of deferred fees, cost, premium and discount as of December 31, 2021 and 2020, respectively.