Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Mar. 31, 2018	Apr. 01, 2017
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 87	$ 92	$ 175	$ 183
Interest costs	122	111	245	223
Expected return on plan assets	(227)	(218)	(452)	(437)
Amortization of prior-year service costs	5	2	8	5
Recognized net actuarial loss	88	101	175	202
Net periodic benefit cost	75	88	151	176
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	2	3	5	6
Interest costs	15	14	30	28
Expected return on plan assets	(13)	(12)	(26)	(24)
Amortization of prior-year service costs	0	0	0	0
Recognized net actuarial loss	4	4	7	8
Net periodic benefit cost	$ 8	$ 9	$ 16	$ 18