Note 3 - Net Loss Per Share - Common Shares Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares shares in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Antidilutive securities (in shares)		7,544	9,087
Share-based Payment Arrangement, Option [Member]
Antidilutive securities (in shares)		6,597	6,522
Contingent Consideration Liability [Member]
Antidilutive securities (in shares)	[1]	947	2,565

[1] Calculated as follows: (a) the contingent consideration liability balance divided by (b) the closing stock price of our common stock.