Securities - Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 643,576	$ 681,510
Unrealized Gains	15,791	12,714
Unrealized Losses	(3,967)	(8,504)
Fair Value	655,400us-gaap_AvailableForSaleSecurities	685,720us-gaap_AvailableForSaleSecurities
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	146,329	155,482
Unrealized Gains	2,711	2,301
Unrealized Losses	(407)	(2,219)
Fair Value	148,633	155,564
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	172,948	174,600
Unrealized Gains	7,885	6,804
Unrealized Losses	(136)	(402)
Fair Value	180,697	181,002
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	240,172	265,678
Unrealized Gains	3,766	2,291
Unrealized Losses	(986)	(2,805)
Fair Value	242,952	265,164
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,792	20,791
Unrealized Gains	167	139
Unrealized Losses	(1,423)	(1,500)
Fair Value	19,536	19,430
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800	800
Unrealized Gains	105	105
Unrealized Losses	0	0
Fair Value	905	905
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	61,515	63,139
Unrealized Gains	1,157	1,074
Unrealized Losses	(1,000)	(1,560)
Fair Value	61,672	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	(15)	(18)
Fair Value	$ 1,005	$ 1,002

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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