Note 2 - Net Income (Loss) Per Share - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 02, 2021	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Net income (loss)	$ 15,989	$ 12,607	$ 10,629	$ 8,167	$ 13,987	$ 13,539	$ 8,559	$ 7,408	$ 47,392	$ 43,493	$ (26,322)
Shares used in basic Net income (loss) per share (in shares)									135,220	132,471	126,564
Dilutive effect of stock options, RSUs, ESPP shares, and equity awards with a market condition or performance condition (in shares)									6,056	4,803	0
Shares used in diluted Net income (loss) per share (in shares)									141,276	137,274	126,564
Net income per share - basic (in dollars per share)	$ 0.12	$ 0.09	$ 0.08	$ 0.06	$ 0.10	$ 0.10	$ 0.06	$ 0.06	$ 0.35	$ 0.33	$ (0.21)
Net income per share - diluted (in dollars per share)	$ 0.11	$ 0.09	$ 0.08	$ 0.06	$ 0.10	$ 0.10	$ 0.06	$ 0.05	$ 0.34	$ 0.32	$ (0.21)
Stock options, RSUs, ESPP shares, and equity awards with a market condition or performance condition excluded as they are antidilutive (in shares)									316	890	7,567