Equity Changes in Accumulated Other Comprehensive Loss, Before Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 27, 2025	Sep. 28, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	$ (4,417)	$ (3,887)	$ (4,980)
Unrealized gains (losses) arising during the period	96	32	1,491
Reclassifications of realized net (gains) losses to net income	(118)	(562)	(398)
AOCI reclassifications to comprehensive income, before tax	904
AOCI before Tax, Attributable to Parent, Ending Balance	(3,535)	(4,417)	(3,887)
Market Value Adjustments for Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(319)	259	804
Unrealized gains (losses) arising during the period	20	(112)	(101)
Reclassifications of realized net (gains) losses to net income	(250)	(466)	(444)
AOCI reclassifications to comprehensive income, before tax	0
AOCI before Tax, Attributable to Parent, Ending Balance	(549)	(319)	259
Unrecognized Pension and Postretirement Medical Expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(2,243)	(2,172)	(3,770)
Unrealized gains (losses) arising during the period	210	25	1,594
Reclassifications of realized net (gains) losses to net income	132	(96)	4
AOCI reclassifications to comprehensive income, before tax	0
AOCI before Tax, Attributable to Parent, Ending Balance	(1,901)	(2,243)	(2,172)
Foreign Currency Translation and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Beginning Balance	(1,855)	(1,974)	(2,014)
Unrealized gains (losses) arising during the period	(134)	119	(2)
Reclassifications of realized net (gains) losses to net income	0	0	42
AOCI reclassifications to comprehensive income, before tax	904
AOCI before Tax, Attributable to Parent, Ending Balance	$ (1,085)	$ (1,855)	$ (1,974)