Note 8 - Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal income tax benefit at statutory rate	$ (547)	$ (1,127)
Adjusted for:
Valuation allowance	475	6,111
Permanent differences and other	72	15
Income tax expense		$ 4,999	$ (5,000)