Pension, Retiree Medical and Savings Plans (Selected Information About Plans with Liability for Service to Date and Total Benefit Liability in Excess of Plan Assets) (Details) - USD ($) $ in Millions	Dec. 26, 2020	Dec. 28, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit, Unfunded plans	$ 854
Domestic Plan [Member]
Selected information for plans with accumulated benefit obligation in excess of plan assets(a)
Obligation for service to date	(5,537)	$ (9,194)
Fair value of plan assets	4,156	8,497
Selected information for plans with projected benefit obligation in excess of plan assets
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	(9,172)	(10,169)
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets	7,088	8,497
Foreign Plan [Member]
Selected information for plans with accumulated benefit obligation in excess of plan assets(a)
Obligation for service to date	(172)	(192)
Fair value of plan assets	123	151
Selected information for plans with projected benefit obligation in excess of plan assets
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	(2,933)	(632)
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets	2,696	512
Retiree Medical Plan
Selected information for plans with projected benefit obligation in excess of plan assets
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	(1,006)	(988)
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 315	$ 302