Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
James Horwich [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 251	$ 251	$ 501	$ 477
Robert E Shaw [Member]
Related Party Transaction [Line Items]
Ownership of Common Stock, Percentage	7.30%		7.30%
Voting Interest of Common Stock, Percentage	3.30%		3.30%
Related Party Transaction, Purchases from Related Party	$ 2,855	$ 1,663	$ 4,570	$ 3,658
Related Party Transaction, Purchases from Related Party, Percentage	3.50%	2.10%	2.90%	2.40%
Robert P Rothman [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 69	$ 67	$ 138	$ 135