Note 6 - Income Taxes - Components of Income Tax Expense Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal	$ 0	$ 0	$ 0
State	65	144	77
International	0	0	0
Current Income Tax Expense (Benefit), Total	$ 65	$ 144	$ 77