Note 10 - Stockholder's Equity - Stock-based 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-based compensation expense	$ 520	$ 901	$ 2,032	$ 2,899
Cost of Sales [Member]
Stock-based compensation expense	23	32	67	124
Research and Development Expense [Member]
Stock-based compensation expense	24	34	124	168
General and Administrative Expense [Member]
Stock-based compensation expense	$ 473	$ 835	$ 1,841	$ 2,607