Equity Changes in Accumulated Other Comprehensive Loss, Before Tax (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 28, 2019	Dec. 29, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	$ (8,459)	$ (4,849)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	1	11
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	79	30
AOCI reclassifications to retained earnings, before tax		(23)
AOCI before Tax, Attributable to Parent, Ending Balance	(8,379)	(4,831)
Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	0	24
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	0
AOCI reclassifications to retained earnings, before tax		(24)
AOCI before Tax, Attributable to Parent, Ending Balance	0	0
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	129	177
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(81)	27
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(60)	(39)
AOCI reclassifications to retained earnings, before tax		1
AOCI before Tax, Attributable to Parent, Ending Balance	(12)	166
Unrecognized Pension and  Postretirement Medical  Expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(7,502)	(4,323)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	139	69
AOCI reclassifications to retained earnings, before tax		0
AOCI before Tax, Attributable to Parent, Ending Balance	(7,363)	(4,254)
Foreign Currency Translation and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(1,086)	(727)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	82	(16)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	0
AOCI reclassifications to retained earnings, before tax		0
AOCI before Tax, Attributable to Parent, Ending Balance	$ (1,004)	$ (743)