Pension and Other Benefit Programs - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
	Mar. 20, 2019	Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
New vesting service year requirement effective January 1, 2012		3 years
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position		$ (4,837)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Increase (Decrease) for Plan Amendment		159
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		410
Pension plans with accumulated benefit obligations in excess of plan assets, projected benefit obligation		17,500	$ 1,100
Pension plans with accumulated benefit obligations in excess of plan assets, accumulated benefit obligation		16,100	1,000
Pension plans with accumulated benefit obligations in excess of plan assets, aggregate fair value of plan assets		13,900	3
Total accumulated pension benefit obligations		$ 17,000	$ 13,300
Total accumulated pension benefit obligations, vested percentage		98.00%	99.00%
Additional Capital Contributions Commitment		$ 1,000
Pension and postretirement medical plans, employer contributions		$ 1,500
Defined contribution plan, contribution rate		50.00%
Savings and investment plans, employees contribution rate		50.00%
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plans, employer contributions		$ 208	$ 162	$ 143
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plans, employer contributions		25	21	20
Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		$ 600
Defined contribution plan, contribution rate		3.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		$ 675
Defined contribution plan, contribution rate		9.00%
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position		$ (3,653)	(1,772)
Defined Benefit Plan, Benefit Obligation, Business Combination		759	0
Acquisition of TFCF		587	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		232	299	358
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation		18,500	12,000
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets		14,800	10,100
Pension and postretirement medical plans, employer contributions		1,461	335
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position		(1,184)	(878)
Defined Benefit Plan, Benefit Obligation, Business Combination		65	0
Acquisition of TFCF		0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		19	31	$ 35
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation		1,900	1,600
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets		800	700
Pension and postretirement medical plans, employer contributions		$ 37	$ 45
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year		7.00%	7.00%	7.00%
Rate of increase to which the cost of benefits is assumed to decline (the ultimate trend rate)		4.25%	4.25%	4.25%
TFCF
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	$ 237
Defined Benefit Plan, Benefit Obligation, Business Combination	824
Acquisition of TFCF	$ 587