Note 15 - Fair Value Measurements (Details Textual) $ in Thousands	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale, Amortized Cost, Total	$ 268,971	$ 301,779
Debt Securities, Available-for-sale, Total	272,839	296,032
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale, Amortized Cost, Total	7,000	5,000
Debt Securities, Available-for-sale, Total	$ 7,182	$ 4,936
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Measurement Input, Discount Rate [Member] \| Minimum [Member]
Debt Securities, Available-for-sale, Measurement Input	5.13
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Measurement Input, Discount Rate [Member] \| Maximum [Member]
Debt Securities, Available-for-sale, Measurement Input	5.63

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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