Casualty, Environmental and Other Reserves - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 27, 2015 claim	Dec. 26, 2014
All Contingencies Reserves [Line Items]
Total reserves	$ 427	$ 418
Casualty
All Contingencies Reserves [Line Items]
Total reserves	273	265
Self-insured retention amount, per occurrence	50
Number of individual claims expected to exceed self insured retention amount	0
Environmental
All Contingencies Reserves [Line Items]
Total reserves	94	94
Environmental impaired sites	250
Other
All Contingencies Reserves [Line Items]
Total reserves	$ 60	$ 59