Fair Value Disclosures of Financial Assets (Balances of Assets Measured At Fair Value) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	$ 910,055	$ 859,362
Total assets measured at fair value on a recurring basis	922,645	871,794
Total assets measured at fair value on a nonrecurring basis	6,996	11,695
Total assets measured at fair value on a nonrecurring basis	47,300	75,300
Total assets measured at fair value on a nonrecurring basis	54,287	86,257
Collateralized Mortgage Obligation ("CMO") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	255,322	328,386
Federal National Mortgage Association ("FNMA") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	461,435	329,354
Federal Home Loan Mortgage Corporation ("FHLMC") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	72,356	95,086
Government National Mortgage Association ("GNMA") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	67,294	63,967
US Government and Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	51,052	39,025
States And Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	3,148	4,190
Reverse Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	(552)	(646)
Trading Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	12,590	12,432
Other Real Estate Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a nonrecurring basis	6,996	11,695
Impaired Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a nonrecurring basis	47,291	74,562
Significant Other Observable Inputs (Level2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	904,557	856,072
Total assets measured at fair value on a nonrecurring basis		86,257
Significant Other Observable Inputs (Level2) [Member] \| Collateralized Mortgage Obligation ("CMO") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	249,272	324,450
Significant Other Observable Inputs (Level2) [Member] \| Federal National Mortgage Association ("FNMA") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	461,435	329,354
Significant Other Observable Inputs (Level2) [Member] \| Federal Home Loan Mortgage Corporation ("FHLMC") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	72,356	95,086
Significant Other Observable Inputs (Level2) [Member] \| Government National Mortgage Association ("GNMA") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	67,294	63,967
Significant Other Observable Inputs (Level2) [Member] \| US Government and Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	51,052	39,025
Significant Other Observable Inputs (Level2) [Member] \| States And Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	3,148	4,190
Significant Other Observable Inputs (Level2) [Member] \| Other Real Estate Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a nonrecurring basis		11,695
Significant Other Observable Inputs (Level2) [Member] \| Impaired Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a nonrecurring basis		74,562
Significant Unobservable Inputs (Level3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	18,088	15,722
Total assets measured at fair value on a nonrecurring basis	54,287
Significant Unobservable Inputs (Level3) [Member] \| Collateralized Mortgage Obligation ("CMO") [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	6,050	3,936
Significant Unobservable Inputs (Level3) [Member] \| Reverse Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	(552)	(646)
Significant Unobservable Inputs (Level3) [Member] \| Trading Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	12,590	12,432
Significant Unobservable Inputs (Level3) [Member] \| Other Real Estate Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a nonrecurring basis	6,996
Significant Unobservable Inputs (Level3) [Member] \| Impaired Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 47,291

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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Carrying amount as of the balance sheet date of all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance; includes real and personal property; equity interests in corporations, partnerships, and joint ventures; and beneficial interests in trusts.

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- Definition

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 Trading Securities which consist of all investments in certain debt and equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for which an entity has elected the fair value option. Trading generally reflects active and frequent buying and selling, and trading securities are generally used with the objective of generating profits on short-term differences in price, but this category of investments may also include items which are not intended to be sold in the near term or for which the fair value option has been elected.

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