Note 6 - Summary of Unrealized and Realized Gains and Losses Recognized in Net Income on Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Equity Securities [Abstract]
Net gains (loss) recognized during the period on equity securities	$ 810	$ 665	$ (796)	$ 1,865
Less: Net gains recognized during the period on equity securities sold during the period	183	970	351	1,599
Net unrealized gains (losses) recognized during the reporting period on equity securities still held at the reporting date	$ 627	$ (305)	$ (1,147)	$ 266