(10) Concentrations of Credit Risk, Significant Customers and Geographic Information - Revenues by location (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Percent of total revenues by Country
United States of America	0.29%	0.21%	0.20%
Germany	0.38%	0.50%	0.59%
Other	0.33%	0.29%	0.21%