Shareholders' Equity (Share Repurchase) (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 28, 2018	Dec. 27, 2017
Equity, Class of Treasury Stock [Line Items]
Purchase of treasury stock	$ 16,186
Number of accumulated shares repurchased (in shares)	44,222	43,151
Share Repurchase Program 2017 [Member]
Equity, Class of Treasury Stock [Line Items]
Share repurchase, authorized amount (in dollars)	$ 200,000
Purchase of treasury stock (in shares)	1,100
Purchase of treasury stock	$ 16,200
Number of accumulated shares repurchased (in shares)	1,300
Value of shares repurchased	$ 19,900
Remaining shares to be repurchased (in dollars)	$ 180,100