Pension, Retiree Medical and Savings Plans (Estimated Future Benefit Payments) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discretionary	[1]	$ 459	$ 0	$ 407
Non-discretionary		200	162	184
Employer contributions/funding		659	162	591
2016		725
2017		780
2018		825
2019		870
2020		925
2021-25		5,270
Retiree Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Discretionary	[1]	0	0	0
Non-discretionary		36	43	64
Employer contributions/funding		36	$ 43	$ 64
2016	[2]	120
2017	[2]	120
2018	[2]	115
2019	[2]	110
2020	[2]	110
2021-25	[2]	485
Years 2022 Through 2026
Defined Benefit Plan Disclosure [Line Items]
Subsidies expected to be received under the 2003 Medicare Act		$ 7
Large Cap Funds In United States Commingled Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Representation As Percentage Of Total US Plan Assets		19.00%	18.00%
Minimum | Years 2017 Through 2021
Defined Benefit Plan Disclosure [Line Items]
Subsidies expected to be received under the 2003 Medicare Act		$ 2
Maximum | Years 2017 Through 2021
Defined Benefit Plan Disclosure [Line Items]
Subsidies expected to be received under the 2003 Medicare Act		$ 3

[1] $388 million in 2014 pertaining to pension lump sum payments.

[2] Expected future benefit payments for our retiree medical plans do not reflect any estimated subsidies expected to be received under the 2003 Medicare Act. Subsidies are expected to be approximately $2-$3 million for each of the years from 2017 through 2021 and approximately $7 million in total for 2022 through 2026.