Loans and allowance for loan losses - Information on PPP loans (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
Institution
loan
item
Sep. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loan amount $ 592,433,000   $ 592,433,000   $ 426,873,000
SBA fee earned 6,307,000 $ 5,594,000 $ 17,622,000 $ 16,515,000  
PPP Loans          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Number of businesses and non profits funded by PPP loans | Institution     1,500    
Number of jobs protected by PPP loans | item     20,000    
Number of loans granted | loan     1,526    
Loan amount 185,137,000   $ 185,137,000    
SBA fee earned     $ 6,584,000    
PPP loan $350,000          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Number of loans granted | loan     1,426    
Loan amount 94,240,000   $ 94,240,000    
SBA fee earned     $ 4,547,000    
PPP loan $350,000 - $2 million          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Number of loans granted | loan     94    
Loan amount 67,795,000   $ 67,795,000    
SBA fee earned     $ 1,853,000    
PPP loan > $2 million          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Number of loans granted | loan     6    
Loan amount $ 23,102,000   $ 23,102,000    
SBA fee earned     $ 184,000