Pension, Retiree Medical and Savings Plans (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						4 Months Ended		12 Months Ended
	Sep. 07, 2019	Jun. 15, 2019	Mar. 23, 2019	Sep. 08, 2018	Jun. 16, 2018	Mar. 24, 2018	Dec. 28, 2019	Dec. 29, 2018	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ (273)	$ 0
Average remaining service period of active plan participants, pension expense										10 years
Defined Benefit Plan, Average Remaining Service Period of Active Plan Participants, Retiree Medical Expense										8 years
Defined Benefit Plan, Average remaining life expectancy of Inactive Plan Participants, Pension Expense										23 years
Pension strategy investment term, years										5 years
Defined Contribution Plan, Cost										$ 197	$ 180	$ 176
Cost Savings Related to Reorganization of U.S. Pension Plans											42
Cost Savings Related to Reorganization of U.S. Pension Plans Net of Tax											$ 27
Cost Savings Related to Reorganization of U.S. Pension Plans Net of Tax, Earnings per Share											$ 0.02
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets										7.10%	7.20%	7.50%
Domestic - Plan A [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax										$ (220)
Pre-tax non-cash settlement charge, after-tax										$ 170
Pre-tax non-cash settlement charge, net of tax, per share										$ 0.12
Domestic-Plan I [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax										$ (53)
Pre-tax non-cash settlement charge, after-tax										$ 41
Pre-tax non-cash settlement charge, net of tax, per share										$ 0.03
Defined benefit plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax										$ 273
Pre-tax non-cash settlement charge, after-tax										$ 211
Pre-tax non-cash settlement charge, net of tax, per share										$ 0.15
Retiree Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets										6.60%	6.50%	7.50%
Forecast [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets									6.80%