Note 4 - Stockholders' Equity - Summary of Recognized Non-cash Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Cost of Sales [Member]
Stock-based compensation expense	$ 111	$ 46	$ 202	$ 66
Research and Development Expense [Member]
Stock-based compensation expense	544	272	1,011	471
Selling and Marketing Expense [Member]
Stock-based compensation expense	702	519	1,439	859
General and Administrative Expense [Member]
Stock-based compensation expense	605	141	995	228
Stock-based compensation expense	$ 1,962	$ 978	$ 3,647	$ 1,624