Note 2 - Concentration of Credit Risk and Major Customers (Details Textual)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020	Sep. 30, 2021 USD ($)	Sep. 30, 2020	Dec. 31, 2020
Excess Cash Balances, Number of High Credit Quality Financial Institutions			2
Customer Concentration Risk [Member] | Revenue from Contract with Customer Benchmark [Member] | Two Customers [Member]
Concentration Risk Number of Customers	2
Concentration Risk, Percentage	36.00%
Customer Concentration Risk [Member] | Revenue from Contract with Customer Benchmark [Member] | One Customer [Member]
Concentration Risk Number of Customers		1	1	1
Concentration Risk, Percentage		23.00%	26.00%	23.00%
Customer Concentration Risk [Member] | Revenue from Contract with Customer Benchmark [Member] | Largest Customer [Member]
Concentration Risk, Percentage	3.00%		3.00%	3.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Two Customers [Member]
Concentration Risk Number of Customers			2
Concentration Risk, Percentage			36.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | One Customer [Member]
Concentration Risk Number of Customers					1
Concentration Risk, Percentage					20.00%
UNITED STATES
Excess Cash Balances, Number of High Credit Quality Financial Institutions			1
Cash, Ending Balance	$ 1,443,000		$ 1,443,000
CHINA
Excess Cash Balances, Number of High Credit Quality Financial Institutions			1
Cash, Ending Balance	378,000		$ 378,000
MEXICO
Cash, Ending Balance	$ 5,000		$ 5,000