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Acquisitions (Narrative) (Details) $ in Thousands			2 Months Ended	3 Months Ended		9 Months Ended
	Oct. 30, 2016 USD ($) store	Aug. 01, 2016 USD ($) store	Oct. 30, 2016 USD ($) store site	Sep. 30, 2017 USD ($)	Sep. 24, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 24, 2016 USD ($)	Dec. 31, 2016 USD ($)
Acquisitions [Line Items]
Purchase price						$ 0	$ 47,547
Goodwill				$ 52,330		52,330		$ 52,330
Mars Super Market [Member]
Acquisitions [Line Items]
Sales				22,200	$ 13,000	68,000
Number of stores acquired | store		5
Purchase price		$ 24,600
Goodwill		$ 13,300
Number of lease obligations assumed		2
Number of new lease agreements due to acquisition		2
Food Lion, LLC [Member]
Acquisitions [Line Items]
Sales				91,100	$ 2,000	280,000
Number of stores acquired | store			38
Number of owned stores acquired | site			8
Purchase price			$ 29,400
Gain on bargain purchase			$ 23,900
Number of lease obligations assumed			30
Food Lion, LLC [Member] | MARYLAND
Acquisitions [Line Items]
Number of stores acquired | store			21
Food Lion, LLC [Member] | DELAWARE
Acquisitions [Line Items]
Number of stores acquired | store			4
Food Lion, LLC [Member] | VIRGINIA
Acquisitions [Line Items]
Number of stores acquired | store			13
Nell's Family Market [Member]
Acquisitions [Line Items]
Sales				$ 4,400		$ 13,100
Number of stores acquired | store	1
Purchase price	$ 13,000
Purchase price payable	3,400
Purchase price payable, term						4 years
Goodwill	$ 3,900		$ 3,900

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