Equity Changes in Accumulated Other Comprehensive Loss, Before 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 before Tax, Attributable to Parent, Beginning Balance	$ (5,221)	$ (6,068)	$ (5,522)	$ (6,374)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	11	(55)	63	162
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	122	67	371	156
AOCI before Tax, Attributable to Parent, Ending Balance	(5,088)	(6,056)	(5,088)	(6,056)
Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	24	28	15	44
Other Comprehensive Income (Loss), before Reclassifications, before Tax	1	(1)	10	(11)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	0	0	(6)
AOCI before Tax, Attributable to Parent, Ending Balance	25	27	25	27
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(197)	141	(108)	(38)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	296	(108)	150	192
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	26	(41)	83	(162)
AOCI before Tax, Attributable to Parent, Ending Balance	125	(8)	125	(8)
Unrecognized Pension and Postretirement Medical Expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(4,690)	(5,638)	(4,906)	(5,859)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0	0	24	5
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	96	108	288	324
AOCI before Tax, Attributable to Parent, Ending Balance	(4,594)	(5,530)	(4,594)	(5,530)
Foreign Currency Translation and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(358)	(599)	(523)	(521)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(286)	54	(121)	(24)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	0	0	0
AOCI before Tax, Attributable to Parent, Ending Balance	$ (644)	$ (545)	$ (644)	$ (545)