Shareholders' Equity - Accumulated Other Comprehensive Income (Loss) - Components and Changes of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (1,732)	$ (1,548)
Other comprehensive income before reclassifications, net of taxes	49	21
Amounts reclassified into income, net of taxes	6	12
Ending balance	(1,676)	(1,515)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,244)	(1,078)
Other comprehensive income before reclassifications, net of taxes	46	40
Amounts reclassified into income, net of taxes	0	0
Ending balance	(1,199)	(1,038)
Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(557)	(571)
Other comprehensive income before reclassifications, net of taxes	0	0
Amounts reclassified into income, net of taxes	8	12
Ending balance	(549)	(559)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	70	103
Other comprehensive income before reclassifications, net of taxes	3	(19)
Amounts reclassified into income, net of taxes	(2)	1
Ending balance	72	84
Available-for-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1)	0
Other comprehensive income before reclassifications, net of taxes	0	0
Amounts reclassified into income, net of taxes	0	0
Ending balance	$ (1)	$ 0