Mergers and acquisitions - Business Acquisition, Pro Forma Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Farmers National
Business Acquisition [Line Items]
Net interest income	$ 59,543	$ 112,804	$ 115,128
Total revenues	92,919	237,258	177,938
Net income	19,097	$ 24,045	38,696
Atlantic Capital Bank
Business Acquisition [Line Items]
Net interest income	57,023		113,610
Total revenues	90,002		176,413
Net income	$ 18,688		$ 37,191