Premises and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Land	$ 13,591	$ 10,501
Buildings and leasehold improvements	41,748	39,150
Furniture and equipment	17,603	15,991
Property, Plant and Equipment, Gross	72,942	65,642
Less accumulated depreciation and amortization	(24,284)	(23,611)
Premises and equipment, net	$ 48,658	$ 42,031