Bank Premises and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 9,390	$ 9,125	$ 7,833
Rental income for leases included in net occupancy expense	2,139	1,949	1,923
Gain (loss) on sale the of bank premises and equipment	168	(820)	10
Gain (loss) on sale of building	1,894	150	$ 910
Weatherford [Member]
Property, Plant and Equipment [Line Items]
Proceeds from Sale of Building	1,385
Gain (loss) on sale of building	560
Orange [Member]
Property, Plant and Equipment [Line Items]
Proceeds from Sale of Building	2,000
Gain (loss) on sale of building	$ (31)
Write down of anticipated building sale		$ 1,000