Note 9 - Intangible Assets, Net (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Schedule of Finite-Lived Intangible Assets [Table Text Block]

	March 31, 2020
	Gross		Accumulated			Intangible
	Amount		amortization			assets, net
Patents	$	7,744	$	(3,697	)	$	4,047
Trademarks		18		(14	)		4
Total intangible assets	$	7,762	$	(3,711	)	$	4,051

	December 31, 2019
	Gross		Accumulated			Intangible
	Amount		amortization			assets, net
Patents	$	7,638	$	(3,560	)	$	4,078
Trademarks		17		(14	)		3
Total intangible assets	$	7,655	$	(3,574	)	$	4,081

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]

2021	$	543
2022		543
2023		543
2024		543
2025		543
thereafter		1,336
	$	4,051