Note 3 - Investment Securities (Details) - Amortized Cost and Estimated Fair Values of Investment Securities - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Note 3 - Investment Securities (Details) - Amortized Cost and Estimated Fair Values of Investment Securities [Line Items]
Held-to-Maturity Securities, Amortized cost	$ 18,688	$ 21,833
Held-to-Maturity Securities, Gross unrealized gains	782	1,037
Held-to-Maturity Securities, Fair value	19,470	22,870
Available-for-Sale Securities:
Available-for-Sale Securities, Amortized cost	731,090	751,482
Available-for-Sale Securities, Gross unrealized gains	22,204	24,880
Available-for-Sale Securities, Gross unrealized losses	(1,258)	(2,217)
Available-for-Sale Securities, Fair value	752,036	774,145
US States and Political Subdivisions Debt Securities [Member]
Note 3 - Investment Securities (Details) - Amortized Cost and Estimated Fair Values of Investment Securities [Line Items]
Held-to-Maturity Securities, Amortized cost	16,991	19,836
Held-to-Maturity Securities, Gross unrealized gains	617	843
Held-to-Maturity Securities, Fair value	17,608	20,679
Available-for-Sale Securities:
Available-for-Sale Securities, Amortized cost	410,887	393,637
Available-for-Sale Securities, Gross unrealized gains	17,005	18,612
Available-for-Sale Securities, Gross unrealized losses	(399)	(452)
Available-for-Sale Securities, Fair value	427,493	411,797
Pass-Through Mortgage Securities [Member]
Note 3 - Investment Securities (Details) - Amortized Cost and Estimated Fair Values of Investment Securities [Line Items]
Held-to-Maturity Securities, Amortized cost	766	856
Held-to-Maturity Securities, Gross unrealized gains	96	110
Held-to-Maturity Securities, Fair value	862	966
Available-for-Sale Securities:
Available-for-Sale Securities, Amortized cost	155,616	130,966
Available-for-Sale Securities, Gross unrealized gains	1,182	1,421
Available-for-Sale Securities, Gross unrealized losses	(572)	(1,206)
Available-for-Sale Securities, Fair value	156,226	131,181
Collateralized Mortgage Obligations [Member]
Note 3 - Investment Securities (Details) - Amortized Cost and Estimated Fair Values of Investment Securities [Line Items]
Held-to-Maturity Securities, Amortized cost	931	1,141
Held-to-Maturity Securities, Gross unrealized gains	69	84
Held-to-Maturity Securities, Fair value	1,000	1,225
Available-for-Sale Securities:
Available-for-Sale Securities, Amortized cost	164,587	226,879
Available-for-Sale Securities, Gross unrealized gains	4,017	4,847
Available-for-Sale Securities, Gross unrealized losses	(287)	(559)
Available-for-Sale Securities, Fair value	$ 168,317	$ 231,167

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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