Segment, Geographic, Product and Significant Customer Information - Product Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Segment Reporting Information [Line Items]
Products	$ 214,877	$ 185,066	$ 146,945
Automated Systems [Member]
Segment Reporting Information [Line Items]
Products	151,401	127,378	102,386
Integrated Systems [Member]
Segment Reporting Information [Line Items]
Products	42,183	43,846	31,579
Materials Characterization Systems [Member]
Segment Reporting Information [Line Items]
Products	$ 21,293	$ 13,842	$ 12,980