Summary of significant accounting policies - Recent accounting standards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loans and leases
Total loans and leases allowance	$ 27,472	$ 28,383	$ 27,344	$ 22,677
Impact to retained earnings	230,515	203,750
Commercial
Loans and leases
Total loans and leases allowance	5,612	8,453	8,734	6,888
Commercial real estate
Loans and leases
Total loans and leases allowance	17,915	15,928	14,559	11,496
Residential real estate
Loans and leases
Total loans and leases allowance	3,072	3,209	3,129	3,226
Consumer
Loans and leases
Total loans and leases allowance	873	$ 793	$ 922	$ 1,067
Accounting Standards Update 2016-13 | Minimum
Error Corrections and Prior Period Adjustments Restatement
Decrease in management estimates	(2,500)
Loans and leases
Impact to retained earnings	2,100
Accounting Standards Update 2016-13 | Maximum
Error Corrections and Prior Period Adjustments Restatement
Decrease in management estimates	(3,000)
Loans and leases
Impact to retained earnings	$ 2,500