Acquisitions Schedule of assets acquired and liabilities assumed (Details) - USD ($) $ in Thousands	Dec. 29, 2017	Aug. 25, 2017	Dec. 30, 2016	Jun. 27, 2016	Dec. 25, 2015
Business Acquisition [Line Items]
Goodwill	$ 173,202		$ 163,784		$ 155,816
Fells Point
Business Acquisition [Line Items]
Current assets (includes cash acquired)		$ 6,971
Goodwill		5,732
Fixed assets		2,459
Current liabilities		(1,295)
Earn-out liability		(4,445)
Total consideration		33,022
Fells Point | Customer relationships
Business Acquisition [Line Items]
Intangible assets		15,100
Fells Point | Trademarks
Business Acquisition [Line Items]
Intangible assets		8,100
Fells Point | Non-compete agreements
Business Acquisition [Line Items]
Intangible assets		$ 400
MT Food
Business Acquisition [Line Items]
Current assets (includes cash acquired)				$ 6,132
Goodwill				11,976
Fixed assets				261
Current liabilities				(3,969)
Earn-out liability				(500)
Total consideration				21,500
MT Food | Customer relationships
Business Acquisition [Line Items]
Intangible assets				7,600
MT Food | Trademarks
Business Acquisition [Line Items]
Intangible assets				0
MT Food | Non-compete agreements
Business Acquisition [Line Items]
Intangible assets				$ 0