Note 10 - Common Stock and Stock-based Compensation Plans - Equity-based Compensation Expense Included in Interim Condensed Consolidated Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Total equity-based compensation expense	$ 2,679	$ 2,845	$ 5,095	$ 5,616
Cost of Revenues [Member]
Total equity-based compensation expense	160	168	296	325
Research and Development, Net [Member]
Total equity-based compensation expense	1,458	1,359	2,820	2,628
Sales and Marketing [Member]
Total equity-based compensation expense	394	423	750	877
General and Administrative [Member]
Total equity-based compensation expense	$ 667	$ 895	$ 1,229	$ 1,786