Note 10 - Net Loss Per Share - Antidilutive Securities Excluded From Computation of Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities (in shares)	1,281	69	1,289	55
Employee Stock Option [Member]
Antidilutive Securities (in shares)	710	66	758	53
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities (in shares)	449	3	422	2
Performance Shares [Member]
Antidilutive Securities (in shares)	49		36
ESPP [Member]
Antidilutive Securities (in shares)	73		73