Cash And Cash Equivalents And Advertising Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Dec. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 34,623	$ 43,689	$ 34,623	$ 43,689	$ 47,917	$ 46,818
Accounts receivable, net	52,835		52,835		56,265
Advertising Expense	2,500	6,100	4,400	6,900
Cost of sales, including advertising, warehousing and distribution expenses	630,805	642,811	1,272,004	1,266,004
Credit Card Receivable [Member]
Cash and Cash Equivalents [Line Items]
Accounts receivable, net	$ 25,400		$ 25,400		26,600
Reclassifications [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		26,107		26,107	26,612	$ 32,165
Accounts receivable, net					$ (26,612)
Cost of sales, including advertising, warehousing and distribution expenses		$ 6,121		$ 6,881