Note 5 - Fair Value Measurements (Detail) - Available For Sale Investment Securities Measured At Fair Value On A Recurring Basis (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Available For Sale Investment Securities	$ 600,556	$ 597,819
Fair Value, Inputs, Level 1 [Member] \| Mutual Funds And Equity Securities [Member]
Available For Sale Investment Securities	612	1,601
Fair Value, Inputs, Level 1 [Member]
Available For Sale Investment Securities	612	1,601
Fair Value, Inputs, Level 2 [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Available For Sale Investment Securities	74,698	96,163
Fair Value, Inputs, Level 2 [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available For Sale Investment Securities	105,573	84,619
Fair Value, Inputs, Level 2 [Member] \| Residential Mortgage Backed Securities [Member]
Available For Sale Investment Securities	414,185	408,863
Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member]
Available For Sale Investment Securities	5,488	6,364
Fair Value, Inputs, Level 2 [Member] \| Commercial Mortgage Backed Securities [Member]
Available For Sale Investment Securities		209
Fair Value, Inputs, Level 2 [Member]
Available For Sale Investment Securities	599,944	596,218
US Government-sponsored Enterprises Debt Securities [Member]
Available For Sale Investment Securities	74,698	96,163
US States and Political Subdivisions Debt Securities [Member]
Available For Sale Investment Securities	105,573	84,619
Residential Mortgage Backed Securities [Member]
Available For Sale Investment Securities	414,185	408,863
Mutual Funds And Equity Securities [Member]
Available For Sale Investment Securities	612	1,601
Corporate Debt Securities [Member]
Available For Sale Investment Securities	5,488	6,364
Commercial Mortgage Backed Securities [Member]
Available For Sale Investment Securities		$ 209

- 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 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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