Note 7 - Income Taxes - Change in Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Balance of unrecognized tax benefits	$ 554,000	$ 843,000
Reductions due to lapse of applicable statute of limitations	(43,000)	(35,000)
Reductions due to tax positions of prior years		(66,000)
Reductions due to settlement with taxing authorities	(300,000)	(300,000)
Additions based on tax positions related to the current year	381,000	112,000
Balance of unrecognized tax benefits	$ 592,000	$ 554,000