Note 7 - Taxes on Income - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reductions due to lapse of statute of limitations	$ (100)	$ (100)	$ (100)
Excluding Interest and Penalties [Member]
Balance at January 1,	399	399
Additions based on tax positions related to the current year	59	55
Additions for tax positions of prior years		4
Reductions due to lapse of statute of limitations	(58)	(59)
Balance at December 31,	$ 400	$ 399	$ 399