Revenue Recognition (Schedule Of Sales By Type Of Product) (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 28, 2019 segment	Sep. 29, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 29, 2018 USD ($) segment	Sep. 30, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Number of reportable segments | segment	1			1
Total net sales		$ 869,076	$ 854,261	$ 2,616,282	$ 2,583,059
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		$ 743,209	$ 731,741	$ 2,243,178	$ 2,221,303
Grocery [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent		85.50%	85.70%	85.70%	86.00%
Pharmacy [Member]
Disaggregation of Revenue [Line Items]
Total net sales		$ 77,568	$ 77,998	$ 233,778	$ 232,913
Pharmacy [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent		8.90%	9.10%	8.90%	9.00%
Fuel [Member]
Disaggregation of Revenue [Line Items]
Total net sales		$ 33,668	$ 27,951	$ 95,751	$ 80,231
Fuel [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent		3.90%	3.30%	3.70%	3.10%
Manufacturing [Member]
Disaggregation of Revenue [Line Items]
Total net sales		$ 14,631	$ 16,571	$ 43,575	$ 48,612
Manufacturing [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent		1.70%	1.90%	1.70%	1.90%