Premises and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Land	$ 10,501	$ 10,501
Buildings and leasehold improvements	39,150	39,251
Furniture and equipment	15,991	15,848
Property, Plant and Equipment, Gross	65,642	65,600
Less accumulated depreciation and amortization	(23,611)	(21,951)
Premises and equipment, net	$ 42,031	$ 43,649