Note 4 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Business Combination, Contingent Consideration, Liability, Total	$ 3,600		$ 3,900
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	(300)	$ 900
AZERDA Commercial Sale Milestone [Member]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 300