Equity and Noncontrolling Interests - Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 2,443	$ 2,546	$ 2,375
Aggregate adjustment for the period, net of tax	23	172	4
Ending balance	2,063	2,443	2,546
AOCI attributable to parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(693)	(842)	(845)
Ending balance	(670)	(693)	(842)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(673)	(854)	(836)
Aggregate adjustment for the period, net of tax	(14)	181	(18)
Ending balance	(687)	(673)	(854)
Foreign currency translation adjustments | Net investment hedging
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4)
Ending balance	(7)	(4)
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(19)	13	(8)
Current period changes in fair value, net of tax	30	(1)	79
Reclassification to income, net of tax	7	(31)	(58)
Ending balance	18	(19)	13
Pension plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1)	(1)	(1)
Net reclassifications to AOCI	0	0	0
Ending balance	$ (1)	$ (1)	$ (1)