Schedule of Revenue by end market (Details)	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Total revenue by end market	100.00%	100.00%
Advanced Industrial
Segment Reporting Information [Line Items]
Total revenue by end market	50.00%	60.00%
Medical
Segment Reporting Information [Line Items]
Total revenue by end market	50.00%	40.00%