Share Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Dec. 30, 2017
Share Data
Common stock, outstanding	81,147		81,147		81,535
Reconciliation of shares for basic and diluted net income per share
Net income	$ 17,030	$ 11,271	$ 32,594	$ 11,427
Weighted average common shares outstanding—basic	81,147	81,479	81,238	81,460
Effect of dilutive securities	1,777	1,509	1,708	1,555
Weighted average common shares outstanding—diluted	82,924	82,988	82,946	83,015
Basic	$ 0.21	$ 0.14	$ 0.40	$ 0.14
Diluted	$ 0.21	$ 0.14	$ 0.39	$ 0.14