Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
James Horwich [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 251	$ 251	$ 752	$ 728
Robert E Shaw [Member]
Related Party Transaction [Line Items]
Ownership of Common Stock, Percentage	7.20%		7.20%
Voting Interest of Common Stock, Percentage	3.30%		3.30%
Related Party Transaction, Purchases from Related Party	$ 2,009	$ 2,119	$ 6,578	$ 5,776
Related Party Transaction, Purchases from Related Party, Percentage	2.50%	2.70%	2.80%	2.50%
Robert P Rothman [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 70	$ 69	$ 208	$ 204