Note 8 - Net Loss Per Share - Antidilutive Securities Excluded From Computation of Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities (in shares)	1,265	1,272	51
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities (in shares)	417	664	42
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities (in shares)	559	432	9
ESPP [Member]
Antidilutive Securities (in shares)	111	133
Performance Shares [Member]
Antidilutive Securities (in shares)	178	43