Note 12 - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Stock Option [Member]
Allocated share-based compensation expense	$ 5,580	$ 4,386	$ 3,084
ESPP [Member]
Allocated share-based compensation expense	502	423	377
Cost of Sales [Member]
Allocated share-based compensation expense	513	386	316
Selling and Marketing Expense [Member]
Allocated share-based compensation expense	1,074	927	610
Research and Development Expense [Member]
Allocated share-based compensation expense	1,285	1,048	754
General and Administrative Expense [Member]
Allocated share-based compensation expense	3,210	2,448	1,781
Allocated share-based compensation expense	6,082	4,809	3,461
Income tax benefits	(1,859)	(1,524)	(847)
Total stock-based compensation expense, net of tax	$ 4,223	$ 3,285	$ 2,614