Note 3 - Securities - Securities Held-to-maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Securities held to maturity, amortized cost	$ 17,353	$ 17,581
Securities held to maturity, gross unrecognized gains	558	533
Securities held to maturity, gross unrecognized losses	(102)	(35)
Securities held to maturity	17,809	18,079
US States and Political Subdivisions Debt Securities [Member]
Securities held to maturity, amortized cost	17,350	17,577
Securities held to maturity, gross unrecognized gains	558	533
Securities held to maturity, gross unrecognized losses	(102)	(35)
Securities held to maturity	17,806	18,075
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities held to maturity, amortized cost	3	4
Securities held to maturity, gross unrecognized gains
Securities held to maturity, gross unrecognized losses
Securities held to maturity	$ 3	$ 4

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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- Definition

Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities measured at amortized cost (held-to-maturity).

+ References

No definition available.

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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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