Note 6 - Investments - Gross Realized Gains and Losses on Available-for-sale Investments, Limited Liability Investment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gross realized gains	$ 193	$ 164	$ 505	$ 380
Gross realized losses	(34)	(223)	(108)	(223)
Net realized gains (losses)	$ 159	$ (59)	$ 397	$ 157

Amount of realized gain (loss) on investment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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