Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment, Net, by Type [Abstract]
Land & land improvements	$ 8,883	$ 8,933
Buildings	38,754	39,638
Furniture and equipment	29,528	28,446
Premises and equipment, gross	77,165	77,017
Less: Accumulated depreciation	(34,855)	(33,570)
Premises and equipment less depreciation, gross	42,310	43,447
Construction in progress	24	46
Total premises and equipment	$ 42,334	$ 43,493