Note 9 - Income Taxes - Change in Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Balance of unrecognized tax benefits	$ 843,000	$ 662,000
Additions based on tax positions of prior years		(7,000)
Additions based on tax positions related to the current year	112,000	188,000
Reductions due to lapse of applicable statute of limitations	(35,000)
Reductions due to tax positions of prior years	(66,000)
Reductions due to settlement with taxing authorities	(300,000)
Balance of unrecognized tax benefits	$ 554,000	$ 843,000