Note 7 - Share-based Compensation - Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Stock compensation expense	$ 1,560	$ 829	$ 3,818	$ 2,179
Research and Development Expense [Member]
Stock compensation expense	291	165	687	400
Selling and Marketing Expense [Member]
Stock compensation expense	256	182	581	507
General and Administrative Expense [Member]
Stock compensation expense	868	429	2,144	1,145
Cost of Sales [Member]
Stock compensation expense	$ 145	$ 53	$ 406	$ 127