Securities - Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 727,426	$ 712,637
Unrealized Gains	12,755	28,181
Unrealized Losses	(15,883)	(3,507)
Fair Value	724,298	737,311
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,008	4,018
Unrealized Gains	8	18
Unrealized Losses	0	0
Fair Value	2,016	4,036
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	181,161	157,965
Unrealized Gains	3,420	5,977
Unrealized Losses	(4,519)	(161)
Fair Value	180,062	163,781
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	179,079	170,223
Unrealized Gains	4,629	11,113
Unrealized Losses	(2,473)	(57)
Fair Value	181,235	181,279
Residential & Multi Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	274,041	308,800
Unrealized Gains	3,195	8,724
Unrealized Losses	(5,899)	(702)
Fair Value	271,337	316,822
Commercial Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	995	1,275
Unrealized Gains	0	29
Unrealized Losses	(12)	0
Fair Value	983	1,304
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,989	17,368
Unrealized Gains	59	26
Unrealized Losses	(1,674)	(2,370)
Fair Value	13,374	15,024
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800	800
Unrealized Gains	0	0
Unrealized Losses	(170)	(200)
Fair Value	630	600
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	73,333	50,667
Unrealized Gains	1,444	2,277
Unrealized Losses	(1,114)	(17)
Fair Value	73,663	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	(22)	0
Fair Value	$ 998	$ 1,538