Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation gain (loss)	$ 9,082	$ (2,976)
Changes in defined benefit plan liabilities	(3,142)	(3,292)
Unrealized holding gains on available-for-sale securities	0	2,638
Total accumulated other comprehensive income (loss)	$ 5,940	$ (3,630)