Note 4 - Concentration of Credit Risk (Details Textual) $ in Thousands		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 USD ($)	Dec. 31, 2019 USD ($)
Accounts Receivable, after Allowance for Credit Loss, Total	[1]	$ 60,330		$ 60,330		$ 53,749	$ 43,619
Revenue from Contract with Customer Benchmark [Member] | Customer Concentration Risk [Member]
Number of Major Customers		0	0	0	0
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Number of Major Customers				1		0
Accounts Receivable [Member] | Customer Concentration Risk [Member] | One Distributor [Member]
Accounts Receivable, after Allowance for Credit Loss, Total		$ 7,100		$ 7,100

[1] Accounts receivable, net is inclusive of accounts receivable, net of allowance for doubtful accounts, short-term unbilled receivables and long-term unbilled receivables.