Revenue Recognition (Schedule Of Sales By Type Of Product) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jul. 01, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jul. 01, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Number of reportable segments | segment			1
Total net sales	$ 871,100	$ 876,569	$ 1,747,206	$ 1,728,798
Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	100.00%	100.00%	100.00%	100.00%
Grocery [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 757,894	$ 768,824	$ 1,525,912	$ 1,518,386
Grocery [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	87.00%	87.60%	87.30%	87.80%
Pharmacy [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 78,271	$ 78,573	$ 156,211	$ 154,823
Pharmacy [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	9.00%	9.00%	8.90%	9.00%
Fuel [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 33,439	$ 27,830	$ 62,084	$ 52,280
Fuel [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	3.80%	3.20%	3.60%	3.00%
Manufacturing [Member]
Disaggregation of Revenue [Line Items]
Total net sales	$ 1,496	$ 1,342	$ 2,999	$ 3,309
Manufacturing [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent	0.20%	0.20%	0.20%	0.20%