Pension, Retiree Medical and Savings Plans (Estimated Future Benefit Payments) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 23, 2019	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Payments for Defined Benefit Plan Settlement					$ 452
Employer contributions/funding			$ 1,495	$ 60
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discretionary			1,417	6	459
Non-discretionary			$ 198	158	200
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year, Description			1615
2019			$ 1,060
2020			960
2021			875
2022			915
2023			950
2024-28			5,265
Employer contributions/funding			1,400	164	659
Retiree Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Discretionary			37	0	0
Non-discretionary			56	56	36
2019	[1]		115
2020	[1]		105
2021	[1]		100
2022	[1]		100
2023	[1]		95
2024-28	[1]		395
Employer contributions/funding			93	$ 56	$ 36
Years 2024 Through 2028
Defined Benefit Plan Disclosure [Line Items]
Subsidies expected to be received under the 2003 Medicare Act			6
Maximum | Years 2019 Through 2023
Defined Benefit Plan Disclosure [Line Items]
Subsidies expected to be received under the 2003 Medicare Act			$ 2
Subsequent Event [Member] | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discretionary		$ 150
Non-discretionary		205
Subsequent Event [Member] | Retiree Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Non-discretionary		$ 40

[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 2019 through 2023 and approximately $6 million in total for 2024 through 2028.