Premises and Equipment - Components of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total cost	$ 78,919	$ 72,227
Less: accumulated depreciation	(36,763)	(35,218)
Net book value	42,156	37,009
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	11,527	10,576
Premises and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	40,936	37,348
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 26,456	$ 24,303