Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balances at beginning of period	$ 17,402	$ 18,753
Aggregate adjustment for the period	(60)	(599)	$ 362
Balances at end of period	17,694	17,402	18,753
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balances at beginning of period	(911)	(434)	(776)
Balances at end of period	(955)	(911)	(434)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balances at beginning of period	(901)	(421)	(778)
Aggregate adjustment for the period	(69)	(480)	357
Balances at end of period	(970)	(901)	(421)
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balances at beginning of period	(11)	(17)	2
Other comprehensive income (loss) before reclassifications, before tax	19	20	(3)
Reclassification to income	11	(16)	(14)
Net tax impact	(4)	2	(2)
Balances at end of period	15	(11)	(17)
Pension and postretirement plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balances at beginning of period	1	4	0
Other comprehensive income (loss) before reclassifications, before tax	0	0	8
Reclassification to income	(1)	(3)	(3)
Net tax impact	0	0	(1)
Balances at end of period	$ 0	$ 1	$ 4