Note 9 - Patents and Trademarks, Net - Accumulated Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accumulated amortization	$ (2,161)	$ (2,078)
Purchased and Licensed Patent Rights [Member]
Accumulated amortization	(555)	(548)
Internally Developed Patents [Member]
Accumulated amortization	(1,471)	(1,400)
Trademarks [Member]
Accumulated amortization	$ (135)	$ (130)