Securities - Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 708,303	$ 712,637
Unrealized Gains	11,248	28,181
Unrealized Losses	(19,020)	(3,507)
Fair Value	700,531	737,311
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,003	4,018
Unrealized Gains	4	18
Unrealized Losses	0	0
Fair Value	2,007	4,036
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	179,875	157,965
Unrealized Gains	3,175	5,977
Unrealized Losses	(5,820)	(161)
Fair Value	177,230	163,781
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	177,503	170,223
Unrealized Gains	4,416	11,113
Unrealized Losses	(2,056)	(57)
Fair Value	179,863	181,279
Residential and Multi Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	258,466	308,800
Unrealized Gains	2,945	8,724
Unrealized Losses	(6,372)	(702)
Fair Value	255,039	316,822
Commercial Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	971	1,275
Unrealized Gains	0	29
Unrealized Losses	(21)	0
Fair Value	950	1,304
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,741	17,368
Unrealized Gains	56	26
Unrealized Losses	(1,640)	(2,370)
Fair Value	14,157	15,024
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800	800
Unrealized Gains	0	0
Unrealized Losses	(24)	(200)
Fair Value	776	600
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	71,924	50,667
Unrealized Gains	652	2,277
Unrealized Losses	(3,063)	(17)
Fair Value	69,513	52,927
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,020	1,521
Unrealized Gains	0	17
Unrealized Losses	(24)	0
Fair Value	$ 996	$ 1,538