Note 12 - Fair Value of Financial Instruments (Detail) - Fair Value of Financial Instruments (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financial Assets
Securities available-for-sale	$ 2,190,296
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Assets
Cash and due from banks	155,525	144,909
Short-term investments	215,794	411,983
Securities held-to-maturity		823,906
Securities available-for-sale	2,190,296	1,291,480
Trading securities	4,758	4,703
Loans, net	7,119,348	7,169,732
Investment in Federal Home Loan Bank stock	37,130	41,272
Warrants	98	104
Financial Liabilities
Deposits	7,431,517	7,389,015
Securities sold under agreement to repurchase	1,244,735	1,361,585
Advances from Federal Home Loan Bank	126,962	146,789
Other borrowings	16,232	14,573
Long-term debt	101,715	98,392
Fair Value, Inputs, Level 1 [Member]
Financial Assets
Cash and due from banks	155,525	144,909
Short-term investments	215,794	411,983
Securities available-for-sale	366,149	526,165
Fair Value, Inputs, Level 2 [Member]
Financial Assets
Securities held-to-maturity		823,906
Securities available-for-sale	1,824,147	765,315
Trading securities	4,758	4,703
Investment in Federal Home Loan Bank stock	37,130	41,272
Financial Liabilities
Securities sold under agreement to repurchase	1,244,735	1,361,585
Advances from Federal Home Loan Bank	126,962	146,789
Long-term debt	101,715	98,392
Fair Value, Inputs, Level 3 [Member]
Financial Assets
Loans, net	7,119,348	7,169,732
Warrants	98	104
Financial Liabilities
Deposits	7,431,517	7,389,015
Other borrowings	$ 16,232	$ 14,573

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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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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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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The fair value amount of long-term debt 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.

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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