Premises and Equipment Net - Components of Premises and Equipment Included in Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 24,894	$ 24,651
Less accumulated depreciation	(14,050)	(13,005)
Premises and equipment, net	10,844	11,646
Land and Improvements
Property, Plant and Equipment [Line Items]
Premises and equipment	2,350	2,350
Buildings and Improvements
Property, Plant and Equipment [Line Items]
Premises and equipment	12,221	12,232
Furniture and Equipment
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 10,323	$ 10,069