Note 4 - Marketable Equity Securities - Realized Gains on Marketable Equity Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Sale proceeds	$ 2,984	$ 1,044	$ 6,833
Cost of securities sold	1,929	669	2,098
Realized gains	1,055	375	4,735
Realized gains, net of taxes	$ 815	$ 278	$ 2,938

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).

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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