(11) Concentrations of Credit Risk, Significant Customers and Geographic Information - Revenue derived from following countries (Details)	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019
Percent of Total Revenues Country
United States of America	23.00%	25.00%
Germany	36.00%	44.00%
Other	41.00%	31.00%