Note 9 - Intangible Assets, Net - Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Intangible assets, gross amount	$ 7,762	$ 7,655
Intangible assets, accumulated amortization	(3,711)	(3,574)
Intangible assets, net	4,051	4,081
Patents [Member]
Intangible assets, gross amount	7,744	7,638
Intangible assets, accumulated amortization	(3,697)	(3,560)
Intangible assets, net	4,047	4,078
Trademarks [Member]
Intangible assets, gross amount	18	17
Intangible assets, accumulated amortization	(14)	(14)
Intangible assets, net	$ 4	$ 3