Basis of Presentation and Significant Accounting Policies (Derivative Financial Instruments) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Contract	Dec. 30, 2017 USD ($) Contract
General Discussion of Derivative Instruments and Hedging Activities [Abstract]
Gain on foreign exchange contracts adjusted to fair value through earnings - less than	$ (100)	$ 100
Foreign exchange contracts
General Discussion of Derivative Instruments and Hedging Activities [Abstract]
Total cost of contracts for Japanese yen (in thousands)	$ 3,194	$ 2,204
Number of contracts | Contract	3	2