Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation loss	$ (10,028)	$ (2,976)
Changes in defined benefit plan liabilities	(3,144)	(3,292)
Unrealized holding gains on available-for-sale securities	0	2,638
Total accumulated other comprehensive income loss	$ (13,172)	$ (3,630)