Segment, Geographic, Product and Significant Customer Information - Product Revenues (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 27, 2014	Dec. 28, 2013	Dec. 29, 2012
Segment Reporting Information [Line Items]
Total product revenues	$ 133,589	$ 107,402	$ 143,827
Automated Systems [Member]
Segment Reporting Information [Line Items]
Total product revenues	108,768	82,924	119,451
Integrated Systems [Member]
Segment Reporting Information [Line Items]
Total product revenues	15,334	11,412	12,379
Materials Characterization Systems [Member]
Segment Reporting Information [Line Items]
Total product revenues	$ 9,487	$ 13,066	$ 11,997