SBA loan servicing activities - Schedule of activity for SBA loan servicing rights (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Beginning of period			$ 8,160
End of period	$ 6,155		6,155
SBA Loan
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Beginning of period	6,614	$ 10,034	8,160	$ 11,280
Additions	100	0	100	530
Amortization	(781)	(865)	(2,327)	(2,641)
End of period	$ 5,933	$ 9,169	$ 5,933	$ 9,169