Casualty, Environmental and Other Reserves - Narrative (Details)	6 Months Ended
	Jun. 26, 2015 USD ($) claim site	Dec. 26, 2014 USD ($)
All Contingencies Reserves [Line Items]
Total reserves	$ 426,000,000	$ 418,000,000
Casualty
All Contingencies Reserves [Line Items]
Total reserves	277,000,000	265,000,000
Self-insured retention amount, per occurrence	$ 50,000,000
Number of individual claims expected to exceed self insured retention amount | claim	0
Environmental
All Contingencies Reserves [Line Items]
Total reserves	$ 95,000,000	94,000,000
Environmental impaired sites | site	254
Other
All Contingencies Reserves [Line Items]
Total reserves	$ 54,000,000	$ 59,000,000