Pension and Other Benefit Programs - Benefit Obligations, Assets, Funded Status and Balance Sheet Impacts Associated with Pension and Postretirement Medical Benefit Plans based upon Actuarial Valuations (Detail) - USD ($) $ in Millions		12 Months Ended
		Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
Fair value of plans' assets
Beginning fair value		$ 13,459
Contributions		1,500
Ending fair value		15,640	$ 13,459
Amounts recognized in the balance sheet
Non-current liabilities		(4,783)	(2,712)
Net balance sheet liability		(4,837)
Pension Plans
Projected benefit obligations
Beginning obligations		(14,500)	(14,532)
Acquisition of TFCF		(759)	0
Service cost		(345)	(350)	$ (368)
Interest cost		(592)	(489)	(447)
Actuarial (loss)/gain	[1]	(2,923)	416
Plan amendments and other		32	(12)
Benefits Paid		534	467
Curtailments		22	0
Ending obligations		(18,531)	(14,500)	(14,532)
Fair value of plans' assets
Beginning fair value		12,728	12,325
Acquisition of TFCF		587	0
Actual return on plan assets		690	579
Contributions		1,461	335
Defined Benefit Plan, Plan Assets, Benefits Paid		(534)	(467)
Expenses and other		(54)	(44)
Ending fair value		14,878	12,728	12,325
Underfunded status of the plans		(3,653)	(1,772)
Amounts recognized in the balance sheet
Non-current assets		5	113
Current liabilities		(54)	(51)
Non-current liabilities		(3,604)	(1,834)
Net balance sheet liability		(3,653)	(1,772)
Postretirement Medical Plans
Projected benefit obligations
Beginning obligations		(1,609)	(1,746)
Acquisition of TFCF		(65)	0
Service cost		(8)	(10)	(11)
Interest cost		(67)	(60)	(56)
Actuarial (loss)/gain	[1]	(234)	166
Plan amendments and other		(11)	(10)
Benefits Paid		48	51
Curtailments		0	0
Ending obligations		(1,946)	(1,609)	(1,746)
Fair value of plans' assets
Beginning fair value		731	696
Acquisition of TFCF		0	0
Actual return on plan assets		33	34
Contributions		37	45
Defined Benefit Plan, Plan Assets, Benefits Paid		(48)	(51)
Expenses and other		(9)	(7)
Ending fair value		762	731	$ 696
Underfunded status of the plans		(1,184)	(878)
Amounts recognized in the balance sheet
Non-current assets		0	0
Current liabilities		(5)	0
Non-current liabilities		(1,179)	(878)
Net balance sheet liability		$ (1,184)	$ (878)

[1] The actuarial loss for fiscal 2019 and the actuarial gain for fiscal 2018 were due to the change in the discount rate from the rate that was used in the preceding fiscal year.