Corporate Premises and Equipment - Classifications of Corporate Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment
Corporate premises and equipment, Gross	$ 79,191	$ 76,412
Less accumulated depreciation	(42,091)	(39,443)
Corporate premises and equipment, net	37,100	36,969
Land
Property, Plant and Equipment
Corporate premises and equipment, Gross	8,300	8,340
Building
Property, Plant and Equipment
Corporate premises and equipment, Gross	36,390	35,586
Equipment, Furniture and Fixtures
Property, Plant and Equipment
Corporate premises and equipment, Gross	$ 34,501	$ 32,486