Note 4 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Combination, Contingent Consideration, Liability, Total	$ 3,900	$ 11,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	916	$ (5,800)	$ 2,600
AZERDA Commercial Sale Milestone [Member]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	(7,100)
Payments for Milestones in Business Combination	$ 8,000