Note 4 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Business Combination, Contingent Consideration, Liability, Total	$ 4,800		$ 4,800		$ 11,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 916	$ 1,300	1,816	$ 2,100
AZERDA Commercial Sale Milestone [Member]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability			(6,200)
Payments for Milestones in Business Combination			$ 8,000