Note 2 - Summary of Significant Accounting Policies (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Number of Major Distributors		3
Accounts Receivable, Allowance for Credit Loss, Ending Balance	$ 50		$ 51
Allowance for Doubtful Accounts, Past Due Period Threshold (Day)	120 days
Inventory Valuation Reserves, Ending Balance	$ 230		$ 247
Operating Lease, Impairment Loss	$ 0	$ 125
Payment for Product Supply Period (Day)	30 days
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)	5 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)	7 years
Computer Equipment and Software [Member]
Property, Plant and Equipment, Useful Life (Year)	3 years
Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life (Year)	7 years
Leasehold Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)	7 years