Securities - Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 697,969	$ 697,738
Unrealized Gains	12,558	9,827
Unrealized Losses	(11,161)	(21,574)
Fair Value	699,366	685,991
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	165,427	185,205
Unrealized Gains	2,409	2,894
Unrealized Losses	(3,064)	(6,474)
Fair Value	164,772	181,625
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	175,279	176,490
Unrealized Gains	6,664	3,770
Unrealized Losses	(382)	(2,317)
Fair Value	181,561	177,943
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	274,168	248,017
Unrealized Gains	2,284	2,410
Unrealized Losses	(4,802)	(7,820)
Fair Value	271,650	242,607
Commercial Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	385
Unrealized Gains	0	0
Unrealized Losses	0	(11)
Fair Value	0	374
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,751	15,744
Unrealized Gains	123	65
Unrealized Losses	(1,162)	(1,734)
Fair Value	14,712	14,075
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800	800
Unrealized Gains	71	0
Unrealized Losses	0	(139)
Fair Value	871	661
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	65,524	70,077
Unrealized Gains	1,007	688
Unrealized Losses	(1,728)	(3,044)
Fair Value	64,803	67,721
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,020	1,020
Unrealized Gains	0	0
Unrealized Losses	(23)	(35)
Fair Value	$ 997	$ 985