Note 3 - Securities - Available-for-sale Debt Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available-for-sale debt securities, amortized cost	$ 299,802	$ 291,586
Available-for-sale debt securities, gross unrealized holding gains	30	881
Available-for-sale debt securities, gross unrealized holding losses	8,969	3,008
Total, fair value	290,863	289,459
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale debt securities, amortized cost	154,461	146,812
Available-for-sale debt securities, gross unrealized holding gains	9	567
Available-for-sale debt securities, gross unrealized holding losses	4,015	1,380
Total, fair value	150,455	145,999
Residential Mortgage Backed Securities [Member]
Available-for-sale debt securities, amortized cost	35,144	36,100
Available-for-sale debt securities, gross unrealized holding gains		73
Available-for-sale debt securities, gross unrealized holding losses	1,183	516
Total, fair value	33,961	35,657
Commercial Mortgage Backed Securities [Member]
Available-for-sale debt securities, amortized cost	76,219	76,396
Available-for-sale debt securities, gross unrealized holding gains	0	0
Available-for-sale debt securities, gross unrealized holding losses	3,145	978
Total, fair value	73,074	75,418
Collateralized Mortgage Backed Securities [Member]
Available-for-sale debt securities, amortized cost	24,666	22,254
Available-for-sale debt securities, gross unrealized holding gains	21	174
Available-for-sale debt securities, gross unrealized holding losses	531	117
Total, fair value	24,156	22,311
Corporate Debt Securities [Member]
Available-for-sale debt securities, amortized cost	4,000	4,000
Available-for-sale debt securities, gross unrealized holding gains		58
Available-for-sale debt securities, gross unrealized holding losses	43
Total, fair value	3,957	4,058
Asset-backed Securities [Member]
Available-for-sale debt securities, amortized cost	2,388	3,100
Available-for-sale debt securities, gross unrealized holding gains		3
Available-for-sale debt securities, gross unrealized holding losses	33	17
Total, fair value	2,355	3,086
Negotiable Certificates of Deposit [Member]
Available-for-sale debt securities, amortized cost	2,924	2,924
Available-for-sale debt securities, gross unrealized holding gains		6
Available-for-sale debt securities, gross unrealized holding losses	19
Total, fair value	$ 2,905	$ 2,930

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Subparagraph (c)
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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