Pension and Other Benefit Programs - Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 410
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	345	$ 350	$ 368
Interest cost	592	489	447
Expected return on plan assets	(978)	(901)	(874)
Amortization of prior-year service costs	13	13	12
Recognized net actuarial loss	260	348	405
Total other costs (benefits)	(113)	(51)	(10)
Net periodic benefit cost	232	299	358
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	10	11
Interest cost	67	60	56
Expected return on plan assets	(56)	(53)	(49)
Amortization of prior-year service costs	0	0	0
Recognized net actuarial loss	0	14	17
Total other costs (benefits)	11	21	24
Net periodic benefit cost	$ 19	$ 31	$ 35