Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2020	Sep. 28, 2019	Oct. 03, 2020	Sep. 28, 2019
Earnings Per Share
Net income	$ 3,162	$ 20,181	$ 3,583	$ 9,550
Shares used in computing basic earnings (loss) per share	43,815	43,358	43,737	43,311
Effect of dilutive securities:
Stock-based awards and convertible debt	513	1,276	517	809
Shares used in computing diluted earnings (loss) per share	44,328	44,634	44,254	44,120
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.07	$ 0.47	$ 0.08	$ 0.22
Diluted (in dollars per share)	$ 0.07	$ 0.45	$ 0.08	$ 0.22
Shares attributable to dilutive effect of conversion of debt securities	100	600	200	300