Amortized Cost and Fair Value of Available-for-Sale Securities by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Security obligations due, amortized cost, One to five years	$ 18,135
Security obligations due, amortized cost, Five to ten years	11,386
Security obligations due, amortized cost, After ten years	7,927
Total security obligations due	37,448
Available for sale, Amortized Cost	280,689	276,326
Security obligations due, Fair value, One to five years	18,342
Security obligations due, Fair value, Five to ten years	11,382
Security obligations due, Fair value, After ten years	3,760
Total Security obligations due, Fair value	33,384
Available for sale, Fair Value	284,271	281,197
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Amortized Cost	123,496
Available for sale, Fair Value	127,937
Collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Amortized Cost	119,739
Available for sale, Fair Value	122,844
Small Business Administration
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Amortized Cost	6	8
Available for sale, Fair Value	$ 6	$ 8

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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