Note 7 - Income Tax Expense - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reductions due to lapse of statute of limitations	$ (100)
Excluding Interest and Penalties [Member]
Balance at the beginning of year	681	$ 477
Additions based on tax positions related to the current year	134	128
Additions for tax positions of prior years	286	173
Reductions due to lapse of statute of limitations	(108)	(97)
Balance at the end of year	$ 993	$ 681