Loans, net and allowance for loan losses - Major Classification of Loans Portfolio Summarized by Credit Quality (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable
Loans	$ 2,181,909	$ 1,938,240
Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	694,551	522,957
Real estate Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	1,099,818	1,011,423
Real estate Residential
Accounts, Notes, Loans and Financing Receivable
Loans	297,880	301,378
Real estate Residential
Accounts, Notes, Loans and Financing Receivable
Loans	297,880	301,378
Consumer
Accounts, Notes, Loans and Financing Receivable
Loans	89,660	102,482
Pass
Accounts, Notes, Loans and Financing Receivable
Loans	2,145,208	1,908,233
Pass | Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	677,234	513,994
Pass | Real estate Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	1,083,864	993,645
Pass | Real estate Residential
Accounts, Notes, Loans and Financing Receivable
Loans	294,627	298,449
Pass | Consumer
Accounts, Notes, Loans and Financing Receivable
Loans	89,483	102,145
Special Mention
Accounts, Notes, Loans and Financing Receivable
Loans	17,521	6,942
Special Mention | Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	10,915	3,837
Special Mention | Real estate Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	6,606	2,508
Special Mention | Real estate Residential
Accounts, Notes, Loans and Financing Receivable
Loans		597
Substandard
Accounts, Notes, Loans and Financing Receivable
Loans	19,180	23,065
Substandard | Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	6,402	5,126
Substandard | Real estate Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	9,348	15,270
Substandard | Real estate Residential
Accounts, Notes, Loans and Financing Receivable
Loans	3,253	2,332
Substandard | Consumer
Accounts, Notes, Loans and Financing Receivable
Loans	$ 177	$ 337