Note 9 - Net Income (Loss) Per Share - Antidilutive Securities Excluded From Computation of Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities (in shares)	51	244	2,988
Employee Stock Option [Member]
Antidilutive Securities (in shares)	42	220	2,575
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities (in shares)	9	24	296
ESPP [Member]
Antidilutive Securities (in shares)			93
Performance Shares [Member]
Antidilutive Securities (in shares)			24