Certain Significant Estimates (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Product Warranty [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 876	$ 847	$ 695
Additions	1,036	1,501	1,459
Deductions	(1,221)	(1,472)	(1,307)
Ending balance	691	876	847
Inventory Valuation Reserves [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	415	471	537
Additions	288	327	470
Deductions	(199)	(383)	(536)
Ending balance	504	415	471
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	910	1,086	900
Additions	775	1,758	159
Deductions	(1,062)	(1,934)	27
Ending balance	623	910	1,086
Customer Allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	2,777	2,151	2,155
Additions	6,608	5,778	5,312
Deductions	(6,028)	(5,152)	(5,316)
Ending balance	$ 3,357	$ 2,777	$ 2,151