Note 6 - Summary of Unrealized and Realized Gains and Losses Recognized in Net Income on Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Equity Securities [Abstract]
Net (loss) gains recognized during the period on equity securities	$ (2,940)	$ 1,021
Less: Net gains recognized during the period on equity securities sold during the period		45
Net unrealized (losses) gains recognized during the reporting period on equity securities still held at the reporting date	$ (2,940)	$ 976

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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