Premises and Equipment - Major Classification (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 32,665	$ 32,163
Less: accumulated depreciation and amortization	14,655	13,881
Premises and equipment, net	18,010	18,282
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	4,986	4,731
Buildings and improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	14,328	14,122
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	1,056	1,226
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	8,506	8,332
Software
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	3,272	3,232
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 517	$ 520