Note 11 - 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	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Total equity-based compensation expense	$ 2,752	$ 2,467	$ 7,847	$ 8,083
Cost of Revenues [Member]
Total equity-based compensation expense	168	155	464	480
Research and Development, Net [Member]
Total equity-based compensation expense	1,494	1,246	4,314	3,874
Sales and Marketing [Member]
Total equity-based compensation expense	362	369	1,112	1,246
General and Administrative [Member]
Total equity-based compensation expense	$ 728	$ 697	$ 1,957	$ 2,483