Note 8 - Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Beginning of year	$ 298,000	$ 421,000	$ 447,000
Current year positions
Prior year positions	(298,000)	(123,000)	(26,000)
End of year	$ 0	$ 298,000	$ 421,000