Note 9 - Contract Assets and Liabilities 1 (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Contract with Customer, Receivable, after Allowance for Credit Loss, Total	$ 876,000	$ 806,000		$ 673,000
License [Member]
Contract with Customer, Liability, Noncurrent	1,733,000	$ 1,767,000	$ 2,000,000
Contract with Customer, Liability, Revenue Recognized	$ 33,000