Note 2 - Investment Securities (Details Textual) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	47
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 26,336		$ 30,418
Available-for-sale Securities, Gross Realized Gains	165	$ 262
Available-for-sale Securities, Gross Realized Losses	$ 105	$ 5
US Government Agencies Debt Securities [Member]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	15
Other than Temporary Impairment Losses, Investments	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 6,497		6,983
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	22
Other than Temporary Impairment Losses, Investments	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 13,798		15,706
Corporate Debt Securities [Member]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	3
Other than Temporary Impairment Losses, Investments	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 2,469		500
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	7
Other than Temporary Impairment Losses, Investments	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 3,572		$ 7,229

This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=82895926&loc=d3e25351-111560

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