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
	Mar. 31, 2019	Mar. 31, 2018
Total equity-based compensation expense	$ 2,416	$ 2,771
Cost of Revenues [Member]
Total equity-based compensation expense	136	157
Research and Development, Net [Member]
Total equity-based compensation expense	1,362	1,269
Sales and Marketing [Member]
Total equity-based compensation expense	356	454
General and Administrative [Member]
Total equity-based compensation expense	$ 562	$ 891