Note 5 - Stockholders' Equity - Allocation of Recognized Period Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allocation of recognized period costs	$ 2,949	$ 2,977	$ 8,737	$ 7,935
Cost of Sales [Member]
Allocation of recognized period costs	1,184	1,191	3,445	3,232
Research and Development Expense [Member]
Allocation of recognized period costs	877	894	2,558	2,251
Selling, General and Administrative Expenses [Member]
Allocation of recognized period costs	$ 888	$ 892	$ 2,734	$ 2,452