Accrued Warranty (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017
Product Warranties Disclosures [Abstract]
Balance at beginning of the period	$ 4,835	$ 3,142
Provision charged to cost of revenue	722	799
Warranty liabilities acquired from acquisitions		419
Use of provision	(560)	(442)
Foreign currency exchange rate changes	57	7
Balance at end of period	$ 5,054	$ 3,925