Note 4 - Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities available-for-sale, amortized costs	$ 311,318	$ 309,802
Securities available-for-sale, gross unrealized gains	1,240	808
Securities available-for-sale, gross unrealized losses	3,235	6,328
Securities available-for-sale, fair values	309,323	304,282
US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized costs	294,609	291,271
Securities available-for-sale, gross unrealized gains	825	492
Securities available-for-sale, gross unrealized losses	3,205	6,165
Securities available-for-sale, fair values	292,229	285,598
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized costs	10,047	11,482
Securities available-for-sale, gross unrealized gains	142	211
Securities available-for-sale, gross unrealized losses	4	0
Securities available-for-sale, fair values	10,185	11,693
Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale, amortized costs	646	845
Securities available-for-sale, gross unrealized gains	65	85
Securities available-for-sale, gross unrealized losses	0	0
Securities available-for-sale, fair values	711	930
Corporate Debt Securities [Member]
Securities available-for-sale, amortized costs	6,016	6,015
Securities available-for-sale, gross unrealized gains	208	20
Securities available-for-sale, gross unrealized losses	26	137
Securities available-for-sale, fair values	6,198	5,898
Other Securities [Member]
Securities available-for-sale, amortized costs		189
Securities available-for-sale, gross unrealized gains		0
Securities available-for-sale, gross unrealized losses		26
Securities available-for-sale, fair values		$ 163

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
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
-Paragraph 1
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