Net Periodic Benefit Cost (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 28, 2015	Mar. 29, 2014	Mar. 28, 2015	Mar. 29, 2014
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 83	$ 71	$ 166	$ 142
Interest costs	131	122	262	244
Expected return on plan assets	(178)	(162)	(356)	(323)
Amortization of prior- year service costs	4	3	8	7
Recognized net actuarial loss/(gain)	61	37	123	73
Net periodic benefit cost	101	71	203	143
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	3	2	7	5
Interest costs	17	17	34	33
Expected return on plan assets	(9)	(9)	(19)	(18)
Amortization of prior- year service costs	(1)	(1)	(1)	(1)
Recognized net actuarial loss/(gain)	2	(2)	5	(4)
Net periodic benefit cost	$ 12	$ 7	$ 26	$ 15