Note 3 - Investment Securities (Detail) - Investment Securities (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Held-to-Maturity Securities Amortized Cost	$ 510,630	$ 525,444
Held-to-Maturity Securities Gross Unrealized Gains	5,918	7,060
Held-to-Maturity Securities Gross Unrealized (Losses)	(129)	(298)
Held-to-Maturity Securities Estimated Fair Value	516,419	532,206
Available-for-Sale Securities Amortized Cost	204,115	171,489
Available-for-Sale Securities Gross Unrealized Gains	988	956
Available-for-Sale Securities Gross Unrealized (Losses)	(52)	(233)
Available-for-Sale Securities Estimated Fair Value	205,051	172,212
US Treasury Securities [Member]
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 Securities Amortized Cost	303,640	308,779
Held-to-Maturity Securities Gross Unrealized Gains	297	712
Held-to-Maturity Securities Gross Unrealized (Losses)	(32)	(154)
Held-to-Maturity Securities Estimated Fair Value	303,905	309,337
Available-for-Sale Securities Amortized Cost	164,300	153,560
Available-for-Sale Securities Gross Unrealized Gains	196	295
Available-for-Sale Securities Gross Unrealized (Losses)	(29)	(228)
Available-for-Sale Securities Estimated Fair Value	164,467	153,627
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Held-to-Maturity Securities Amortized Cost	51	62
Held-to-Maturity Securities Gross Unrealized Gains	2	1
Held-to-Maturity Securities Estimated Fair Value	53	63
Available-for-Sale Securities Amortized Cost	23,998	2,280
Available-for-Sale Securities Gross Unrealized Gains	354	277
Available-for-Sale Securities Gross Unrealized (Losses)	(19)
Available-for-Sale Securities Estimated Fair Value	24,333	2,557
US States and Political Subdivisions Debt Securities [Member]
Held-to-Maturity Securities Amortized Cost	206,319	211,673
Held-to-Maturity Securities Gross Unrealized Gains	5,619	6,333
Held-to-Maturity Securities Gross Unrealized (Losses)	(97)	(144)
Held-to-Maturity Securities Estimated Fair Value	211,841	217,862
Other Securities [Member]
Held-to-Maturity Securities Amortized Cost	620	930
Held-to-Maturity Securities Estimated Fair Value	620	930
Available-for-Sale Securities Amortized Cost	15,817	15,649
Available-for-Sale Securities Gross Unrealized Gains	438	384
Available-for-Sale Securities Gross Unrealized (Losses)	(4)	(5)
Available-for-Sale Securities Estimated Fair Value	$ 16,251	$ 16,028

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details

- 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.

+ References+ Details

- Definition

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.

+ References+ Details

- 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.

+ References

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+ Details

- Definition

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.

+ References+ Details

- Definition

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.

+ References+ Details

- Definition

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.

+ References+ Details