Changes in Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning Balance	$ (3,345)	$ (3,880)	$ (3,528)	$ (3,979)
Unrealized gains (losses) arising during the period	(9)	(26)	0	17
Reclassifications of realized net (gains) losses to net income	92	42	266	98
AOCI, Ending Balance	(3,262)	(3,864)	(3,262)	(3,864)
Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning Balance	14	16	8	26
Unrealized gains (losses) arising during the period	1	(5)	7	(11)
Reclassifications of realized net (gains) losses to net income	0	0	0	(4)
AOCI, Ending Balance	15	11	15	11
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning Balance	(156)	91	(62)	(25)
Unrealized gains (losses) arising during the period	240	(66)	106	126
Reclassifications of realized net (gains) losses to net income	20	(26)	60	(102)
AOCI, Ending Balance	104	(1)	104	(1)
Unrecognized Pension and Postretirement Medical Expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning Balance	(2,912)	(3,525)	(3,067)	(3,651)
Unrealized gains (losses) arising during the period	(2)	0	19	(10)
Reclassifications of realized net (gains) losses to net income	72	68	206	204
AOCI, Ending Balance	(2,842)	(3,457)	(2,842)	(3,457)
Foreign Currency Translation and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning Balance	(291)	(462)	(407)	(329)
Unrealized gains (losses) arising during the period	(248)	45	(132)	(88)
Reclassifications of realized net (gains) losses to net income	0	0	0	0
AOCI, Ending Balance	$ (539)	$ (417)	$ (539)	$ (417)