Acquisition of Business (Narrative) (Details) $ in Thousands				2 Months Ended		3 Months Ended	4 Months Ended	5 Months Ended	12 Months Ended
	Oct. 30, 2016 USD ($) store	Aug. 01, 2016 USD ($) store	Aug. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Oct. 30, 2016 USD ($) store site	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)
Acquisitions [Line Items]
Purchase price									$ 0	$ 63,632	$ 0
Gain on bargain purchase						$ 23,879			0	23,879	$ 0
Goodwill				$ 52,330		$ 52,330	$ 52,330	$ 52,330	52,330	$ 52,330
Mars Super Market [Member]
Acquisitions [Line Items]
Sales								$ 38,000	91,500
Number of stores acquired | store		5
Purchase price		$ 24,600
Goodwill		$ 13,255
Number of lease obligations assumed		2
Number of new lease agreements due to acquisition		2
Goodwill deductible for tax purposes		$ 13,300
Food Lion, LLC [Member]
Acquisitions [Line Items]
Sales							$ 92,500		369,200
Number of stores acquired | store					38
Number of owned stores acquired | site					8
Purchase price					$ 29,400
Gain on bargain purchase	$ 23,879
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				$ 3,000					$ 17,600
Number of stores acquired | store	1
Purchase price	$ 13,000
Purchase price payable	3,400
Purchase price payable, term									4 years
Goodwill	3,913				$ 3,913
Goodwill deductible for tax purposes	$ 3,900				$ 3,900
C&S Wholesale Grocers [Member]
Acquisitions [Line Items]
Purchase price			$ 7,900
Goodwill			0
Land			1,900
Buildings			5,900
Equipment			$ 112