Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 638,365	$ 681,510
Unrealized Gains	10,545	12,714
Unrealized Losses	(8,901)	(8,504)
Fair Value	640,009	685,720
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	151,385	155,482
Unrealized Gains	2,176	2,301
Unrealized Losses	(1,691)	(2,219)
Fair Value	151,870	155,564
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	177,405	174,600
Unrealized Gains	5,489	6,804
Unrealized Losses	(764)	(402)
Fair Value	182,130	181,002
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	231,535	265,678
Unrealized Gains	1,496	2,291
Unrealized Losses	(4,312)	(2,805)
Fair Value	228,719	265,164
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,792	20,791
Unrealized Gains	193	139
Unrealized Losses	(1,223)	(1,500)
Fair Value	19,762	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	55,428	63,139
Unrealized Gains	831	1,074
Unrealized Losses	(892)	(1,560)
Fair Value	55,367	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	(19)	(18)
Fair Value	$ 1,001	$ 1,002