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, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities (in shares)	1,272	51	244
Employee Stock Option [Member]
Antidilutive Securities (in shares)	664	42	220
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities (in shares)	432	9	24
ESPP [Member]
Antidilutive Securities (in shares)	133
Performance Shares [Member]
Antidilutive Securities (in shares)	43