Amortized Cost and Fair Value of Available-For-Sale Securities, Including Gross Unrealized Gains and Losses (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 356,640	$ 332,942
Unrealized Gains	5,659	5,432
Unrealized Losses	(10,845)	(12,257)
Fair Value	351,454us-gaap_AvailableForSaleSecurities	326,117us-gaap_AvailableForSaleSecurities
U.S. Agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33,934	34,604
Unrealized Gains	39	11
Unrealized Losses	(731)	(1,017)
Fair Value	33,242	33,598
Single Issue Trust Preferred Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	55,837	55,822
Unrealized Losses	(8,749)	(9,685)
Fair Value	47,088	46,137
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	31,370	5,000
Unrealized Gains	214	109
Unrealized Losses	(49)
Fair Value	31,535	5,109
Mortgage-backed Agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	98,829	102,506
Unrealized Gains	618	470
Unrealized Losses	(727)	(857)
Fair Value	98,720	102,119
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	222	226
Unrealized Gains	6	19
Unrealized Losses	(7)	(6)
Fair Value	221	239
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	131,448	134,784
Unrealized Gains	4,782	4,823
Unrealized Losses	(582)	(692)
Fair Value	135,648	138,915
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,000
Fair Value	$ 5,000

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

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-Publisher FASB

-Name Accounting Standards Codification

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

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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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