Basis of Presentation and General Information (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018	Dec. 29, 2018	Dec. 28, 2018	Dec. 29, 2017
Basis Of Presentation And General Information [Line Items]
Revenue recognized as a result of change in contract liability	$ 4,300,000	$ 5,000,000	$ 8,300,000	$ 9,800,000
Deferred commissions						$ 1,200,000	$ 1,400,000
Commissions expense	300,000	300,000	500,000	500,000
Impairment loss recognized to capitalization of deferred commission	0	$ 0	0	$ 0
Additional operating liabilities	7,613,000		7,613,000		$ 9,000,000
Additional operating ROU	$ 7,613,000		$ 7,613,000		$ 9,000,000
Minimum [Member]
Basis Of Presentation And General Information [Line Items]
Business relationship agreement period			6 months
Maximum [Member]
Basis Of Presentation And General Information [Line Items]
Business relationship agreement period			12 months
Customer contract period			12 months