Note 2 - Concentration of Credit Risk and Major Customers (Details Textual) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020	Jun. 30, 2021 USD ($)	Jun. 30, 2020	Dec. 31, 2020
Excess Cash Balances, Number of High Credit Quality Financial Institutions			2
Concentration Risk, Number of Divisions	2	2	2	2
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Division One of Largest Customer [Member]
Concentration Risk, Percentage	23.00%	20.00%	24.00%	22.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Division Two of Largest Customer [Member]
Concentration Risk, Percentage	2.00%	3.00%	3.00%	2.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Divisions One and Two of Largest Customer [Member]
Concentration Risk, Percentage	25.00%	23.00%	27.00%	24.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Largest Customer [Member]
Concentration Risk, Percentage	2.00%	3.00%	3.00%	3.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Largest Customer [Member]
Concentration Risk, Percentage			19.00%		20.00%
UNITED STATES
Excess Cash Balances, Number of High Credit Quality Financial Institutions			1
Cash, Ending Balance	$ 1,253		$ 1,253
CHINA
Excess Cash Balances, Number of High Credit Quality Financial Institutions			1
Cash, Ending Balance	$ 274		$ 274