Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 04, 2020	Jun. 29, 2019	Jul. 04, 2020	Jun. 29, 2019
Earnings (loss) per share:
Net income (loss)	$ (1,823)	$ (16,029)	$ 421	$ (10,631)
Shares used in computing basic earnings (loss) per share	43,761	43,386	43,699	43,287
Effect of dilutive securities:
Stock-based awards and convertible debt			520
Shares used in computing diluted earnings (loss) per share	43,761	43,386	44,219	43,287
Earnings (loss) per share:
Basic (in dollars per share)	$ (0.04)	$ (0.37)	$ 0.01	$ (0.25)
Diluted (in dollars per share)	$ (0.04)	$ (0.37)	$ 0.01	$ (0.25)
Shares excluded from computation of diluted earning (loss) per share	300	600		600
Shares attributable to dilutive effect of conversion of debt securities	0		200
RSUs and MSUs
Earnings (loss) per share:
Shares excluded from computation of diluted earning (loss) per share	400	0	300	500