Casualty, Environmental and Other Reserves (Loss Contingencies Accrual) (Details) - USD ($) $ in Millions	Dec. 25, 2015	Dec. 26, 2014	Dec. 27, 2013	Dec. 28, 2012
Contingencies [Line Items]
Current	$ 131	$ 142
Long-term	269	276
Casualty [Member]
Contingencies [Line Items]
Current	69	76
Long-term	200	189
Total	269	265	$ 280	$ 325
Personal Injury [Member]
Contingencies [Line Items]
Current	57	68
Long-term	147	123
Total	204	191
Asbestos [Member]
Contingencies [Line Items]
Current	9	5
Long-term	44	51
Total	53	56
Occupational [Member]
Contingencies [Line Items]
Current	3	3
Long-term	9	15
Total	12	18
Environmental [Member]
Contingencies [Line Items]
Current	42	48
Long-term	40	46
Total	82	94	100	88
Other Reserves [Member]
Contingencies [Line Items]
Current	20	18
Long-term	29	41
Total	49	59	71	64
Casualty, Environmental and Other [Member]
Contingencies [Line Items]
Current	131	142
Long-term	269	276
Total	$ 400	$ 418	$ 451	$ 477