Revenue Recognition (Schedule Of Sales By Type Of Product) (Details) $ in Thousands	3 Months Ended
	Mar. 30, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Number of reportable segments | segment	1
Total net sales	$ 876,718	$ 876,106
Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	100.00%	100.00%
Grocery [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 766,901	$ 768,019
Grocery [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	87.50%	87.70%
Pharmacy [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 81,781	$ 77,940
Pharmacy [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	9.30%	8.90%
Fuel [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 26,465	$ 28,645
Fuel [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	3.00%	3.30%
Manufacturing [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 1,571	$ 1,502
Manufacturing [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	0.20%	0.10%