Premises and Equipment, Net - Summary of Premises and Equipment (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 45,930,000	$ 45,981,000
Less: accumulated depreciation	20,771,000	20,062,000
Premises and equipment, net	25,159,000	25,919,000
Land and improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	8,556,000	8,556,000
Buildings [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	24,727,000	24,564,000
Furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 12,647,000	$ 12,861,000