Casualty, Environmental and Other Reserves (Loss Contingencies Roll Forward) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 28, 2012		Dec. 30, 2011		Dec. 31, 2010
Loss Contingency Accrual [Roll Forward]
Balance, beginning of period	$ 519		$ 541		$ 621
Charged to Expense	122		132		137
Change in Estimate					(49)	[1]
Payments	(164)		(154)		(168)
Balance, end of period	477		519		541
Casualty Reserves [Member]
Loss Contingency Accrual [Roll Forward]
Balance, beginning of period	372		375		459
Charged to Expense	51		68		70
Change in Estimate	0		0		(49)	[1]
Payments	(98)		(71)		(105)
Balance, end of period	325		372		375
Environmental Reserves [Member]
Loss Contingency Accrual [Roll Forward]
Balance, beginning of period	83		107		97
Charged to Expense	35		23		36
Change in Estimate					0	[1]
Payments	(30)		(47)		(26)
Balance, end of period	88		83		107
Other Reserves [Member]
Loss Contingency Accrual [Roll Forward]
Balance, beginning of period	64	[2]	59	[2]	65	[2]
Charged to Expense	36	[2]	41	[2]	31	[2]
Change in Estimate					0	[1],[2]
Payments	(36)	[2]	(36)	[2]	(37)	[2]
Balance, end of period	$ 64	[2]	$ 64	[2]	$ 59	[2]

[1] Change in estimate in 2010 is the result of continued safety improvements and decreasing claim trends for both personal injury and occupational injuries.

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