Equity and Noncontrolling Interests - Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 2,546	$ 2,375	$ 2,718
Aggregate adjustment for the period, net of tax	172	4	(249)
Current period changes in fair value, net of tax	(32)	21
Net reclassifications to AOCI	0	0	(1)
Ending balance	2,443	2,546	2,375
AOCI attributable to parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(842)	(845)	(627)
Current period changes in fair value, net of tax	(32)	21
Net reclassifications to AOCI			(1)
Ending balance	(693)	(842)	(845)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(854)	(836)	(617)
Aggregate adjustment for the period, net of tax	181	(18)	(219)
Ending balance	(673)	(854)	(836)
Foreign currency translation adjustments | Net investment hedging
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	76
Ending balance	(4)	76
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	13	(8)	(8)
Current period changes in fair value, net of tax	(1)	79	6
Reclassification to income, net of tax	(31)	(58)	(6)
Ending balance	(19)	13	(8)
Pension plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1)	(1)	(2)
Net reclassifications to AOCI	0	0	1
Ending balance	$ (1)	$ (1)	$ (1)