Note 9 - Stock-based Compensation Expense Recognized for Stock Options Granted (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Research and Development Expense [Member]
Allocated Share-based Compensation Expense	$ 650	$ 114	$ 106
General and Administrative Expense [Member]
Allocated Share-based Compensation Expense	1,514	345	49
Allocated Share-based Compensation Expense	$ 2,164	$ 459	$ 155