Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 87	$ 90	$ 262	$ 273
Interest costs	122	113	367	336
Expected return on plan assets	(225)	(219)	(677)	(656)
Amortization of prior-year service costs	3	3	11	8
Recognized net actuarial loss	86	101	261	303
Net periodic benefit cost	73	88	224	264
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	3	3	8	9
Interest costs	15	14	45	42
Expected return on plan assets	(13)	(13)	(39)	(37)
Amortization of prior-year service costs	0	0	0	0
Recognized net actuarial loss	3	4	10	12
Net periodic benefit cost	$ 8	$ 8	$ 24	$ 26