Note 2 - Summary of Significant Accounting Policies - Summary of Stock Compensation Expense by Income Statement Account (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock compensation expense	$ 582	$ 671	$ 674
Cost of Sales [Member]
Stock compensation expense	71	88	101
General and Administrative Expense [Member]
Stock compensation expense	398	420	433
Selling and Marketing Expense [Member]
Stock compensation expense	55	116	108
Research and Development Expense [Member]
Stock compensation expense	$ 58	$ 47	$ 32