Pension, Retiree Medical and Savings Plans (Estimated Future Benefit Payments) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015	Dec. 31, 2018
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Payments for Defined Benefit Plan Settlement			$ 452
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discretionary		$ 6	459	$ 0
Non-discretionary		158	200	162
2018		890
2019		985
2020		825
2021		875
2022		925
2023-27		5,210
Retiree Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Discretionary		0	0	0
Non-discretionary		56	$ 36	$ 43
2018	[1]	120
2019	[1]	120
2020	[1]	110
2021	[1]	110
2022	[1]	105
2023-27	[1]	455
Years 2023 Through 2027
Defined Benefit Plan Disclosure [Line Items]
Subsidies expected to be received under the 2003 Medicare Act		6
Maximum | Years 2018 Through 2022
Defined Benefit Plan Disclosure [Line Items]
Subsidies expected to be received under the 2003 Medicare Act		$ 2
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions in 2018					$ 175
Scenario, Forecast [Member] | Retiree Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions in 2018					75
Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions in 2018					1,400
Funded Plan [Member] | Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions in 2018					800
Unfunded Plan [Member] | Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions in 2018					$ 700

[1] 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 million for each of the years from 2018 through 2022 and approximately $6 million in total for 2023 through 2027.