Schedule of Revenue by end market (Details)	3 Months Ended		9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Segment Reporting Information [Line Items]
Total revenue by end market	100.00%	100.00%	100.00%	100.00%
Advanced Industrial
Segment Reporting Information [Line Items]
Total revenue by end market	50.00%	50.00%	50.00%	55.00%
Medical
Segment Reporting Information [Line Items]
Total revenue by end market	50.00%	50.00%	50.00%	45.00%