Note 6 - Investment Securities Available-for-sale (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	$ 382,296	$ 390,475
Investment securities available-for-sale, gross unrealized holding gains	1,759	2,186
Investment securities available-for-sale, gross unrealized holding losses	(6,952)	(7,879)
Investment securities available-for-sale, amortized cost	387,489	396,168
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	70,646	76,650
Investment securities available-for-sale, gross unrealized holding gains	25	36
Investment securities available-for-sale, gross unrealized holding losses	(1,847)	(2,118)
Investment securities available-for-sale, amortized cost	72,468	78,732
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	75,728	72,295
Investment securities available-for-sale, gross unrealized holding gains	714	614
Investment securities available-for-sale, gross unrealized holding losses	(272)	(398)
Investment securities available-for-sale, amortized cost	75,286	72,079
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	142,230	145,301
Investment securities available-for-sale, gross unrealized holding gains	448	561
Investment securities available-for-sale, gross unrealized holding losses	(2,080)	(2,241)
Investment securities available-for-sale, amortized cost	143,862	146,981
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	77,106	77,415
Investment securities available-for-sale, gross unrealized holding gains	67	109
Investment securities available-for-sale, gross unrealized holding losses	(1,775)	(1,846)
Investment securities available-for-sale, amortized cost	78,814	79,152
Collateralized Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	2,423	2,281
Investment securities available-for-sale, gross unrealized holding gains	295	263
Investment securities available-for-sale, gross unrealized holding losses	(748)	(891)
Investment securities available-for-sale, amortized cost	2,876	2,909
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	8,056	8,030
Investment securities available-for-sale, gross unrealized holding gains	29	16
Investment securities available-for-sale, gross unrealized holding losses	(40)	(57)
Investment securities available-for-sale, amortized cost	8,067	8,071
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale	6,107	8,503
Investment securities available-for-sale, gross unrealized holding gains	181	587
Investment securities available-for-sale, gross unrealized holding losses	(190)	(328)
Investment securities available-for-sale, amortized cost	$ 6,116	$ 8,244

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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