Note 9 - Stock-based Compensation Plan - Allocation of Share-based Compensation Expense (Details) - Restricted Stock [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Allocation of Share-based Compensation Expense	$ 208	$ 213	$ 395	$ 396
Cost of Sales [Member]
Allocation of Share-based Compensation Expense
Selling and Marketing Expense [Member]
Allocation of Share-based Compensation Expense	3	4	6	4
Research and Development Expense [Member]
Allocation of Share-based Compensation Expense	11	12	21	15
General and Administrative Expense [Member]
Allocation of Share-based Compensation Expense	$ 194	$ 197	$ 368	$ 377