Schedule of Geographic Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018
Segment Reporting Information [Line Items]
Revenue	$ 155,145	$ 150,400	$ 312,331	$ 297,365
United States
Segment Reporting Information [Line Items]
Revenue	62,010	60,467	126,770	118,580
Germany
Segment Reporting Information [Line Items]
Revenue	18,838	21,012	42,315	41,081
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	35,971	23,347	66,741	50,407
China
Segment Reporting Information [Line Items]
Revenue	15,392	18,367	30,500	33,970
Rest of Asia-Pacific
Segment Reporting Information [Line Items]
Revenue	20,702	24,987	41,149	49,707
Other Countries
Segment Reporting Information [Line Items]
Revenue	$ 2,232	$ 2,220	$ 4,856	$ 3,620