Equity Changes in Accumulated Other Comprehensive Loss, Before Tax (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance		$ (8,478)	$ (4,834)	$ (8,459)	$ (4,849)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(70)	51	(264)	9
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		54	14	229	94
AOCI reclassifications to retained earnings, before tax					(23)
AOCI before Tax, Attributable to Parent, Ending Balance		(8,494)	(4,769)	(8,494)	(4,769)
Accumulated Net Gain (Loss) from Market Value Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	[1]	158	57	129	201
Other Comprehensive Income (Loss), before Reclassifications, before Tax	[1]	(87)	40	44	(20)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	(78)	(55)	(180)	(116)
AOCI reclassifications to retained earnings, before tax	[1]				(23)
AOCI before Tax, Attributable to Parent, Ending Balance	[1]	(7)	42	(7)	42
Unrecognized Pension and  Postretirement Medical  Expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance		(7,268)	(4,163)	(7,502)	(4,323)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(6)	(37)	(49)	(18)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		132	69	409	210
AOCI reclassifications to retained earnings, before tax					0
AOCI before Tax, Attributable to Parent, Ending Balance		(7,142)	(4,131)	(7,142)	(4,131)
Foreign Currency Translation and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance		(1,368)	(728)	(1,086)	(727)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		23	48	(259)	47
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0	0	0	0
AOCI reclassifications to retained earnings, before tax					0
AOCI before Tax, Attributable to Parent, Ending Balance		$ (1,345)	$ (680)	$ (1,345)	$ (680)

[1] Primarily reflects market value adjustments for cash flow hedges.