Casualty, Environmental and Other Reserves (Environmental and Other) (Details) (USD $) In Millions, unless otherwise specified	Dec. 28, 2012		Dec. 30, 2011		Dec. 31, 2010		Dec. 25, 2009
Contingencies [Line Items]
Other reserves	$ 477		$ 519		$ 541		$ 621
Environmental Reserves [Member]
Contingencies [Line Items]
Environmental impaired site	248
Other reserves	88		83		107		97
Other Reserves [Member]
Contingencies [Line Items]
Other reserves	$ 64	[1]	$ 64	[1]	$ 59	[1]	$ 65	[1]

[1] Separation liabilities and freight rate dispute reserves have been reclassified to other current liabilities and other long-term liabilities.