Note 7 - Fair Value of Financial Instruments - Assets Measured on a Recurring Basis Using Significant Unobservable Inputs (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Collateralized Debt Obligations [Member]
Balance	$ 561	$ 1,961	$ 489	$ 1,820
Unrealized gains (losses)	(14)	525	58	666
Proceeds from sales		(970)		(970)
Realized losses		(548)		(548)
Balance	547	968	547	968
Corporate Debt Securities [Member]
Balance	3,090	3,024	3,086	2,971
Unrealized gains (losses)	(7)	55	(3)	108
Proceeds from sales
Realized losses
Balance	$ 3,083	$ 3,079	$ 3,083	$ 3,079

Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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-Subparagraph (c)(1)
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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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