Premises and Equipment - Components of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total cost	$ 102,843	$ 78,838
Less: accumulated depreciation	(39,205)	(36,682)
Net book value	63,638	42,156
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	14,033	11,527
Premises and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	55,862	40,850
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 32,948	$ 26,461