Note 2 - Net Income Per Share - Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Net income	$ 10,629	$ 8,559	$ 18,796	$ 15,967
Shares used in basic Net income per share (in shares)	134,857	132,206	134,555	131,599
Dilutive effect of stock options, RSUs, ESPP shares, and equity awards with a market condition or performance condition (in shares)	4,345	5,015	4,196	4,534
Shares used in diluted Net income per share (in shares)	139,202	137,221	138,751	136,133
Basic (in dollars per share)	$ 0.08	$ 0.06	$ 0.14	$ 0.12
Diluted (in dollars per share)	$ 0.08	$ 0.06	$ 0.14	$ 0.12
Stock options, RSUs, ESPP shares, and equity awards with a market condition or performance condition excluded as they are antidilutive (in shares)	579	73	658	210