Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 579,878	$ 681,510
Unrealized Gains	11,778	12,714
Unrealized Losses	(4,323)	(8,504)
Fair Value	587,333	685,720
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	145,440	155,482
Unrealized Gains	2,102	2,301
Unrealized Losses	(533)	(2,219)
Fair Value	147,009	155,564
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	174,367	174,600
Unrealized Gains	6,291	6,804
Unrealized Losses	(229)	(402)
Fair Value	180,429	181,002
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	184,471	265,678
Unrealized Gains	1,825	2,291
Unrealized Losses	(1,949)	(2,805)
Fair Value	184,347	265,164
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,793	20,791
Unrealized Gains	179	139
Unrealized Losses	(936)	(1,500)
Fair Value	19,036	19,430
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800	800
Unrealized Gains	360	105
Unrealized Losses	0	0
Fair Value	1,160	905
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	53,987	63,139
Unrealized Gains	1,021	1,074
Unrealized Losses	(649)	(1,560)
Fair Value	54,359	62,653
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,020	1,020
Unrealized Gains	0	0
Unrealized Losses	(27)	(18)
Fair Value	$ 993	$ 1,002