Note 4 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Business Combination, Contingent Consideration, Liability, Total	$ 4,300		$ 4,300		$ 11,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ (500)	$ (8,000)	1,316	$ (5,900)
AZERDA Commercial Sale Milestone [Member]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability			6,700
Payments for Milestones in Business Combination			$ 8,000