Basis of Presentation and General Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017	Dec. 29, 2017	Dec. 30, 2016
Basis Of Presentation And General Information [Line Items]
Revenue recognized as a result of change in contract liability	$ 4,200,000	$ 5,800,000	$ 14,000,000	$ 17,100,000
Deferred commissions					$ 1,400,000	$ 1,800,000
Commissions expense	100,000	200,000	700,000	1,200,000
Impairment loss recognized to capitalization of deferred commission	$ 0	$ 0	$ 0	$ 0
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