Note 3 - Investment Securities Available for Sale - Amortized Cost and Estimated Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Investment securities available for sale, amortized cost	$ 112,683	$ 103,249
Investment securities available for sale, gross unrealized gains	605	100
Investment securities available for sale, gross unrealized losses	(959)	(1,754)
Investment securities available for sale	112,329	101,595
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities available for sale, amortized cost	81,137	76,207
Investment securities available for sale, gross unrealized gains	100	11
Investment securities available for sale, gross unrealized losses	(821)	(1,307)
Investment securities available for sale	80,416	74,911
US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale, amortized cost	31,546	27,042
Investment securities available for sale, gross unrealized gains	505	89
Investment securities available for sale, gross unrealized losses	(138)	(447)
Investment securities available for sale	$ 31,913	$ 26,684

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=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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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
-Name Accounting Standards Codification
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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