Certain Significant Estimates (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Product Warranty [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 691	$ 876	$ 847
Additions	1,448	1,036	1,501
Deductions	(1,437)	(1,221)	(1,472)
Ending balance	702	691	876
Inventory Valuation Reserves [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	504	415	471
Additions	383	288	327
Deductions	(431)	(199)	(383)
Ending balance	456	504	415
Allowance For Doubtful Accounts [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	623	910	1,086
Additions	155	775	1,758
Deductions	(246)	(1,062)	(1,934)
Ending balance	532	623	910
Customer Allowances [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	3,357	2,777	2,151
Additions	6,575	6,608	5,778
Deductions	(8,382)	(6,028)	(5,152)
Ending balance	$ 1,550	$ 3,357	$ 2,777