Cash And Cash Equivalents And Advertising Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Dec. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 50,215	$ 37,633	$ 47,917	$ 46,818
Accounts receivable, net	48,452		56,265
Advertising Expense	1,900	760
Cost of sales, including advertising, warehousing and distribution expenses	641,199	623,193
Credit Card Receivable [Member]
Cash and Cash Equivalents [Line Items]
Accounts receivable, net	$ 31,400		26,600
Reclassifications [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		25,338	26,612	$ 32,165
Accounts receivable, net			$ (26,612)
Cost of sales, including advertising, warehousing and distribution expenses		$ 760