Note 6 - Investments - Gross Realized Gains and Losses on Available-for-sale Investments, Limited Liability Investment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Gross realized gains	$ 59	$ 51
Gross realized losses	(5)	0
Net realized gains	$ 54	$ 51

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 https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration