Revenue Recognition (Schedule Of Sales By Type Of Product) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 26, 2020	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Disaggregation of Revenue [Line Items]
Total net sales	$ 1,025,690	$ 1,002,387	$ 1,098,704	$ 985,820	$ 902,392	$ 876,222	$ 887,967	$ 876,718	$ 4,112,601	$ 3,543,299	$ 3,509,270
Revenue Benchmark [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Concentration percent									100.00%	100.00%	100.00%
Grocery [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Total net sales									$ 3,627,898	$ 3,068,754	$ 3,063,218
Concentration percent									88.20%	86.60%	87.30%
Pharmacy [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Total net sales									$ 356,630	$ 337,233	$ 314,584
Concentration percent									8.70%	9.50%	9.00%
Fuel [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Total net sales									$ 117,800	$ 127,828	$ 125,993
Concentration percent									2.90%	3.60%	3.60%
Manufacturing [Member] | Revenue Benchmark [Member] | Product Concentration Risk [Member]
Disaggregation of Revenue [Line Items]
Total net sales									$ 10,273	$ 9,484	$ 5,475
Concentration percent									0.20%	0.30%	0.10%