Note 2 - Concentration of Credit Risk and Major Customers (Details Textual) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020	Dec. 31, 2020
Excess Cash Balances, Number of High Credit Quality Financial Institutions	2
Cash, Ending Balance	$ 982
Concentration Risk, Number of Divisions	2	2
Customer Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Percentage	29.00%	26.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Division One of Largest Customer [Member]
Concentration Risk, Percentage	25.00%	24.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Division Two of Largest Customer [Member]
Concentration Risk, Percentage	4.00%	2.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Largest Customer [Member]
Concentration Risk, Percentage	4.00%	3.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Largest Customer [Member]
Concentration Risk, Percentage	23.00%		20.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Another Customer [Member]
Concentration Risk, Percentage	13.00%		10.00%
UNITED STATES
Excess Cash Balances, Number of High Credit Quality Financial Institutions	1
CHINA
Excess Cash Balances, Number of High Credit Quality Financial Institutions	1
Cash, Ending Balance	$ 369