Pension, Retiree Medical and Savings Plans (Components of Benefit Expense) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	$ 227	$ 308	$ 19
Domestic - Plan A [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement/curtailment losses (a)	$ (205)	$ 220
Pre-tax non-cash settlement charge, net of tax, per share	$ 0.11	$ 0.12
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax	$ 158	$ 170
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Pre-tax non-cash settlement charge, net of tax, per share		$ 0.12
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		$ 170
United States Pension Plan of US Entity, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	434	381	431
Interest cost	435	543	482
Expected return on plan assets	(929)	(892)	(943)
Amortization of prior service cost/(credits)	12	10	3
Amortization of net losses/(gains)	196	161	179
Settlement/curtailment losses (a)	213	296	8
Special termination benefits	19	1	36
Defined Benefit Plan, Other Cost (Credit)	(54)	119	(235)
Total	380	500	196
International
Defined Benefit Plan Disclosure [Line Items]
Service cost	86	73	92
Interest cost	85	97	93
Expected return on plan assets	(202)	(188)	(197)
Amortization of net losses/(gains)	61	32	45
Settlement/curtailment losses (a)	19	12	6
Special termination benefits	0	0	2
Defined Benefit Plan, Other Cost (Credit)	(37)	(47)	(51)
Total	49	26	41
Retiree Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	25	23	32
Interest cost	25	36	34
Expected return on plan assets	(16)	(18)	(19)
Amortization of prior service cost/(credits)	(12)	(19)	(20)
Amortization of net losses/(gains)	(23)	(27)	(8)
Settlement/curtailment losses (a)	0	0	0
Special termination benefits	0	0	1
Defined Benefit Plan, Other Cost (Credit)	(26)	(28)	(12)
Total	(1)	(5)	$ 20
Domestic-Plan I [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement/curtailment losses (a)		$ 53
Pre-tax non-cash settlement charge, net of tax, per share		$ 0.03
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		$ 41
Defined benefit plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	$ 158
Pre-tax non-cash settlement charge, net of tax, per share	$ 0.11	$ 0.03
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		$ 41