Note 3 - Net Loss Per Share - Common Shares Excluded from Calculation of Diluted Net (Loss) Income Per Share (Details) - shares shares in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Antidilutive securities (in shares)		9,087	5,842
Share-based Payment Arrangement, Option [Member]
Antidilutive securities (in shares)		6,522	3,483
Contingent Consideration Liability [Member]
Antidilutive securities (in shares)	[1]	2,565	2,359

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