Litigation, Commitments and Contingencies - Leases (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) item	Dec. 25, 2016 USD ($)	Dec. 27, 2015 USD ($)
Lease disclosures
Payments received from sublease	$ 7.4	$ 7.5	$ 6.5
Total lease expense	$ 45.0	$ 45.0	$ 36.2
Office, retail and commissary space
Lease disclosures
Operating leases, average term in years	5 years
Number of renewals | item	1
Tractors and trailers
Lease disclosures
Operating leases, average term in years	7 years