Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Earnings Per Share
Net income	$ 20,181	$ 27,761	$ 9,550	$ 68,446
Shares used in computing basic earnings per share	43,358	43,256	43,311	43,177
Effect of dilutive securities:
Stock-based awards and convertible debt	1,276	938	809	958
Shares used in computing diluted earnings (loss) per share	44,634	44,194	44,120	44,135
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.47	$ 0.64	$ 0.22	$ 1.59
Diluted (in dollars per share)	$ 0.45	$ 0.63	$ 0.22	$ 1.55
Shares attributable to dilutive effect of conversion of debt securities	600	200	300	200