Note 3 - Investment Securities (Detail) - Amortized cost and fair value of investment securities classified as held-to-maturity and available-for-sale: (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	$ 496,141	$ 525,444
Held-to-Maturity Securities Gross Unrealized Gains	5,276	7,060
Held-to-Maturity Securities Gross Unrealized (Losses)	(839)	(298)
Held-to-Maturity Securities Estimated Fair Value	500,578	532,206
Available-for-Sale
Available-for-Sale Securities Amortized Cost	190,920	171,489
Available-for-Sale Securities Gross Unrealized Gains	808	956
Available-for-Sale Securities Gross Unrealized (Losses)	(386)	(233)
Available-for-Sale Securities Estimated Fair Value	191,342	172,212
US Treasury Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost		4,000
Held-to-Maturity Securities Gross Unrealized Gains		14
Held-to-Maturity Securities Estimated Fair Value		4,014
US Government Agencies Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	288,098	308,779
Held-to-Maturity Securities Gross Unrealized Gains	135	712
Held-to-Maturity Securities Gross Unrealized (Losses)	(679)	(154)
Held-to-Maturity Securities Estimated Fair Value	287,554	309,337
Available-for-Sale
Available-for-Sale Securities Amortized Cost	152,708	153,560
Available-for-Sale Securities Gross Unrealized Gains	65	295
Available-for-Sale Securities Gross Unrealized (Losses)	(292)	(228)
Available-for-Sale Securities Estimated Fair Value	152,481	153,627
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	49	62
Held-to-Maturity Securities Gross Unrealized Gains	1	1
Held-to-Maturity Securities Estimated Fair Value	50	63
Available-for-Sale
Available-for-Sale Securities Amortized Cost	20,436	2,280
Available-for-Sale Securities Gross Unrealized Gains	287	277
Available-for-Sale Securities Gross Unrealized (Losses)	(89)
Available-for-Sale Securities Estimated Fair Value	20,634	2,557
US States and Political Subdivisions Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	207,374	211,673
Held-to-Maturity Securities Gross Unrealized Gains	5,140	6,333
Held-to-Maturity Securities Gross Unrealized (Losses)	(160)	(144)
Held-to-Maturity Securities Estimated Fair Value	212,354	217,862
Available-for-Sale
Available-for-Sale Securities Amortized Cost	2,989
Available-for-Sale Securities Gross Unrealized (Losses)	(1)
Available-for-Sale Securities Estimated Fair Value	2,988
Other Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	620	930
Held-to-Maturity Securities Estimated Fair Value	620	930
Available-for-Sale
Available-for-Sale Securities Amortized Cost	14,787	15,649
Available-for-Sale Securities Gross Unrealized Gains	456	384
Available-for-Sale Securities Gross Unrealized (Losses)	(4)	(5)
Available-for-Sale Securities Estimated Fair Value	$ 15,239	$ 16,028

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- Definition

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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This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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- Definition

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

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This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

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As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

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As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

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