Note 8 - Commitments and Contingencies (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Lease, Weighted Average Discount Rate, Percent	3.80%	5.50%
Operating Lease, Weighted Average Remaining Lease Term (Year)	4 years	1 year 36 days
Operating Lease, Expense	$ 142,000	$ 130,000
Cost of Sales [Member]
Operating Lease, Expense	61,000	54,000
General and Administrative Expense [Member]
Operating Lease, Expense	52,000	52,000
Research and Development Expense [Member]
Operating Lease, Expense	29,000	$ 24,000
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset	3,261,000
Operating Lease, Liability, Total	$ 945,000