Fair Value of Financial Instruments - Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Carrying (Reported) Amount
Assets:
Cash and due from banks	$ 101,460	$ 73,312
Interest-bearing time deposits	38,443	52,851
Investment securities available for sale	513,343	518,491
Investment securities held to maturity	361,020	427,909
Mortgage loans held for sale	22,300	17,864
Loans	2,832,843	2,642,517
Federal Reserve Bank and Federal Home Loan Bank stock	32,785	31,270
Interest rate swap asset	6,300	5,665
Interest receivable	16,367	17,723
Liabilities:
Deposits	3,346,383	3,134,655
Borrowings:
Federal funds purchased	18,862
Securities sold under repurchase agreements	141,828	156,305
Federal Home Loan Bank advances	94,238	138,095
Subordinated debentures, revolving credit lines and term loans	112,161	194,974
Interest rate swap liability	9,766	7,797
Interest payable	1,841	2,925
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and due from banks	101,460	73,312
Interest-bearing time deposits	38,443	52,851
Liabilities:
Deposits	2,478,706	2,195,679
Significant Other Observable Inputs (Level 2)
Assets:
Investment securities available for sale	495,015	497,653
Investment securities held to maturity	366,590	428,737
Mortgage loans held for sale	22,300	17,864
Federal Reserve Bank and Federal Home Loan Bank stock	32,785	31,270
Interest rate swap asset	6,300
Interest receivable	16,367	17,723
Liabilities:
Deposits	865,793	944,078
Borrowings:
Federal funds purchased	18,862
Securities sold under repurchase agreements	142,318	157,342
Federal Home Loan Bank advances	97,357	141,693
Subordinated debentures, revolving credit lines and term loans	62,133	142,632
Interest rate swap liability	9,766
Interest payable	1,841	2,925
Significant Unobservable Inputs (Level 3)
Assets:
Investment securities available for sale	18,328	20,838
Investment securities held to maturity	11,584	13,732
Loans	2,852,614	2,658,227
Interest rate swap asset		5,665
Borrowings:
Interest rate swap liability		$ 7,797

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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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