Note 10 - Net Loss Per Share - Antidilutive Securities Excluded From Computation of Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities (in shares)	1,089	42	1,227	37
Employee Stock Option [Member]
Antidilutive Securities (in shares)	607	42	707	31
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities (in shares)	411		419	6
Performance Shares [Member]
Antidilutive Securities (in shares)	24		19
ESPP [Member]
Antidilutive Securities (in shares)	47		82