Casualty, Environmental and Other Reserves - Schedule of Claims Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2016	Dec. 25, 2015	Dec. 26, 2014
Casualty, Environmental and Other
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	$ 400	$ 418	$ 451
Charged to Expense	128	142	176
Change in Estimate	(28)
Payments	(126)	(160)	(209)
Balance end of period	374	400	418
Casualty Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	269	265	280
Charged to Expense	52	60	89
Change in Estimate	(28)
Payments	(64)	(56)	(104)
Balance end of period	229	269	265
Environmental Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	82	94	100
Charged to Expense	46	45	57
Change in Estimate	0
Payments	(33)	(57)	(63)
Balance end of period	95	82	94
Other Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	49	59	71
Charged to Expense	30	37	30
Change in Estimate	0
Payments	(29)	(47)	(42)
Balance end of period	$ 50	$ 49	$ 59