Pension, Retiree Medical and Savings Plans (Selected Financial Information for Pension and Retiree Medical Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Pension Plans, Defined Benefit
Change in fair value of plan assets
Employer contributions/funding	$ 507	$ 672	$ 1,615
Retiree Medical Plan
Change in projected benefit obligation
Obligation at beginning of year	988	996
Service cost	25	23	32
Interest cost	25	36	34
Plan amendments	(25)
Experience loss	81	36
Other, including foreign currency adjustment	1	2
Obligation at end of year	1,006	988	996
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(89)	(105)
Change in fair value of plan assets
Fair value at beginning of year	302	285
Actual return on plan assets	47	78
Employer contributions/funding	55	44	93
Defined Benefit Plan, Plan Assets, Benefits Paid	(89)	(105)
Fair value at end of year	315	302	285
Funded status	(691)	(686)
Amounts recognized
Other current liabilities	(51)	(58)
Other liabilities	(640)	(628)
Net amount recognized	(691)	(686)
Amounts included in accumulated other comprehensive loss (pre-tax)
Net loss/(gain)	(212)	(285)
Prior service (credit)/cost	(45)	(32)
Total	(257)	(317)
Changes recognized in net loss/(gain) included in other comprehensive loss
Net loss/(gain) arising in current year	50	(24)
Amortization and settlement recognition	23	27
Foreign currency translation loss/(gain)		(1)
Total	73	2
Domestic Plan [Member]
Change in projected benefit obligation
Obligation at beginning of year	15,230	13,807
Service cost	434	381	431
Interest cost	435	543	482
Plan amendments	(221)	15
Experience loss	2,042	2,091
Settlement/curtailment	(808)	(1,268)
Special termination benefits	19	2
Obligation at end of year	16,753	15,230	13,807
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(378)	(341)
Change in fair value of plan assets
Fair value at beginning of year	14,302	12,258
Actual return on plan assets	1,908	3,101
Employer contributions/funding	387	550
Defined Benefit Plan, Plan Assets, Benefits Paid	(378)	(341)
Defined Benefit Plan, Plan Assets, Payment for Settlement	(754)	(1,266)
Fair value at end of year	15,465	14,302	12,258
Funded status	(1,288)	(928)
Amounts recognized
Other assets	797	744
Other current liabilities	(53)	(52)
Other liabilities	(2,032)	(1,620)
Net amount recognized	(1,288)	(928)
Amounts included in accumulated other comprehensive loss (pre-tax)
Net loss/(gain)	4,116	3,516
Prior service (credit)/cost	(119)	114
Total	3,997	3,630
Changes recognized in net loss/(gain) included in other comprehensive loss
Net loss/(gain) arising in current year	1,009	(120)
Amortization and settlement recognition	(409)	(457)
Total	600	(577)
Accumulated benefit obligation at end of year	15,949	14,255
Foreign Plan [Member]
Change in projected benefit obligation
Obligation at beginning of year	3,753	3,098
Service cost	86	73	92
Interest cost	85	97	93
Plan amendments	(17)	1
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	2	2
Experience loss	467	515
Settlement/curtailment	(24)	(31)
Other, including foreign currency adjustment	170	98
Obligation at end of year	4,430	3,753	3,098
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(92)	(100)
Change in fair value of plan assets
Fair value at beginning of year	3,732	3,090
Actual return on plan assets	401	551
Employer contributions/funding	120	122
Participant contributions	2	2
Defined Benefit Plan, Plan Assets, Benefits Paid	(92)	(100)
Defined Benefit Plan, Plan Assets, Payment for Settlement	(29)	(31)
Other, including foreign currency adjustment	169	98
Fair value at end of year	4,303	3,732	$ 3,090
Funded status	(127)	(21)
Amounts recognized
Other assets	110	99
Other current liabilities	(1)	(1)
Other liabilities	(236)	(119)
Net amount recognized	(127)	(21)
Amounts included in accumulated other comprehensive loss (pre-tax)
Net loss/(gain)	1,149	914
Prior service (credit)/cost	(19)
Total	1,130	914
Changes recognized in net loss/(gain) included in other comprehensive loss
Net loss/(gain) arising in current year	268	152
Amortization and settlement recognition	(75)	(44)
Foreign currency translation loss/(gain)	42	26
Total	235	134
Accumulated benefit obligation at end of year	$ 4,108	$ 3,441