Note 15 - Stock-based Compensation - Compensation Related to Stock-based Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total stock-based compensation expense	$ 8,760	$ 5,157	$ 3,955
Tax effect on stock-based compensation expense	604	617	440
Net effect of stock-based compensation expense	8,156	4,540	3,515
Cost of Sales [Member]
Total stock-based compensation expense	3,369	2,400	1,753
Selling and Marketing Expense [Member]
Total stock-based compensation expense	452	247	123
General and Administrative Expense [Member]
Total stock-based compensation expense	$ 4,939	$ 2,510	$ 2,079