Equity and Noncontrolling Interests - Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 1,535	$ 2,189	$ 2,717
Aggregate adjustment for the period, net of tax	37	(89)	(38)
Realized and unrealized gains (losses) on derivatives	20	(20)	(1)
Net reclassifications to AOCI	(1)	0	2
Ending balance	2,718	1,535	2,189
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(634)	(558)	(523)
Aggregate adjustment for the period, net of tax	17	(76)	(35)
Ending balance	(617)	(634)	(558)
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(28)	(8)	(7)
Realized and unrealized gains (losses) on derivatives	22	(34)	(5)
Reclassification to income, net of tax	(2)	14	4
Ending balance	(8)	(28)	(8)
Pension plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(3)	(3)	(1)
Net reclassifications to AOCI	1	0	(2)
Ending balance	(2)	(3)	(3)
AOCI attributable to parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(665)	(569)	(531)
Realized and unrealized gains (losses) on derivatives	20	(20)	(1)
Net reclassifications to AOCI	(1)		2
Ending balance	$ (627)	$ (665)	$ (569)