Casualty, Environmental and Other Reserves (Environmental and Other) (Details) (USD $) In Millions, unless otherwise specified	Dec. 26, 2014 sites	Dec. 27, 2013	Dec. 28, 2012	Dec. 30, 2011
Environmental Reserves [Member]
Contingencies [Line Items]
Loss Contingency Accrual	$ 94	$ 100	$ 88	$ 83
Environmental impaired site	250
Other Reserves [Member]
Contingencies [Line Items]
Loss Contingency Accrual	$ 59	$ 71	$ 64	$ 64