Note 12 - Equity-based Compensation - Summary of Stock-based Compensation Expense Included in Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock-based compensation expense	$ 940	$ 710	$ 2,628	$ 1,227
Research and Development Expense [Member]
Stock-based compensation expense	51	63	100	142
Selling and Marketing Expense [Member]
Stock-based compensation expense	153	62	247	113
General and Administrative Expense [Member]
Stock-based compensation expense	$ 736	$ 585	$ 2,281	$ 972