Other real estate owned - Summary of Other Real Estate Owned (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Real Estate [Roll Forward]
Balance at beginning of period	$ 15,091	$ 15,521	$ 18,939	$ 12,643
Transfers from loans	573	1,535	1,579	3,565
Transfers (to) from premises and equipment	0	0	(841)	2,640
Proceeds from sale of other real estate owned	(1,411)	(854)	(5,561)	(2,718)
Gain on sale of other real estate owned	119	260	464	582
Loans provided for sales of other real estate owned	0	0	0	(166)
Write-downs and partial liquidations	(1,624)	(386)	(1,832)	(470)
Balance at end of period	$ 12,748	$ 16,076	$ 12,748	$ 16,076