Schedule of Geographic Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 146,965	$ 108,974
UNITED STATES
Segment Reporting Information [Line Items]
Revenue	58,113	47,211
GERMANY
Segment Reporting Information [Line Items]
Revenue	20,069	14,298
Rest Of Europe
Segment Reporting Information [Line Items]
Revenue	27,060	13,582
CHINA
Segment Reporting Information [Line Items]
Revenue	15,603	11,475
Rest of Asia-Pacific
Segment Reporting Information [Line Items]
Revenue	24,720	19,865
Other Countries
Segment Reporting Information [Line Items]
Revenue	$ 1,400	$ 2,543