Equity Changes in Accumulated Other Comprehensive Loss, Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Oct. 02, 2021	Oct. 03, 2020	Sep. 28, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent, Beginning Balance	$ 2,380	$ 1,842	$ 1,752
Unrealized gains (losses) arising during the period	(416)	604	794
Reclassifications of realized net (gains) losses to net income	(180)	(66)	(21)
AOCI reclassifications to retained earnings, tax			(683)
AOCI Tax, Attributable to Parent, Ending Balance	1,784	2,380	1,842
Market Value Adjustments for Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent, Beginning Balance	40	(29)	(41)
Unrealized gains (losses) arising during the period	(8)	8	(31)
Reclassifications of realized net (gains) losses to net income	10	61	43
AOCI reclassifications to retained earnings, tax			0
AOCI Tax, Attributable to Parent, Ending Balance	42	40	(29)
Unrecognized Pension and Postretirement Medical Expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent, Beginning Balance	2,201	1,756	1,690
Unrealized gains (losses) arising during the period	(358)	572	797
Reclassifications of realized net (gains) losses to net income	(190)	(127)	(64)
AOCI reclassifications to retained earnings, tax			(667)
AOCI Tax, Attributable to Parent, Ending Balance	1,653	2,201	1,756
Foreign Currency Translation and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent, Beginning Balance	139	115	103
Unrealized gains (losses) arising during the period	(50)	24	28
Reclassifications of realized net (gains) losses to net income	0	0	0
AOCI reclassifications to retained earnings, tax			(16)
AOCI Tax, Attributable to Parent, Ending Balance	$ 89	$ 139	$ 115