Note 9 - Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Balance	$ 7,210	$ 5,976
Additions to current period tax positions	1,020	1,234
Balance	$ 8,230	$ 7,210