Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 88	$ 91
Interest costs	123	112
Expected return on plan assets	(225)	(219)
Amortization of prior-year service costs	3	3
Recognized net actuarial loss	87	101
Net periodic benefit cost	76	88
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	3	3
Interest costs	15	14
Expected return on plan assets	(13)	(12)
Amortization of prior-year service costs	0	0
Recognized net actuarial loss	3	4
Net periodic benefit cost	$ 8	$ 9