Casualty, Environmental and Other Reserves - Schedule of Claims Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 30, 2016	Dec. 25, 2015
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	$ 374	$ 400	$ 418
Charged to Expense	114	128	142
Change in Estimate		(28)
Payments	(114)	(126)	(160)
Balance end of period	374	374	400
Casualty Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	229	269	265
Charged to Expense	43	52	60
Change in Estimate		(28)
Payments	(44)	(64)	(56)
Balance end of period	228	229	269
Environmental Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	95	82	94
Charged to Expense	26	46	45
Change in Estimate		0
Payments	(31)	(33)	(57)
Balance end of period	90	95	82
Other Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	50	49	59
Charged to Expense	45	30	37
Change in Estimate		0
Payments	(39)	(29)	(47)
Balance end of period	$ 56	$ 50	$ 49