Note 6 - Fair Value Measurements - Reconciles Net Loss to Unrealized Loss on Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Net gain (loss) recognized during the period on equity securities	$ 4,840	$ (1,153)
Less: Net gain recognized during the period on equity securities sold during the period	(237)	(96)
Unrealized gain (loss) recognized during the reporting period on equity securities still held at the reporting date	$ 4,603	$ (1,057)

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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