Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			$ 17,694
Aggregate adjustment for the period	$ (69)	$ 30	(50)	$ 102
Ending Balance	16,841	17,078	16,841	17,078
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(933)	(864)	(955)	(911)
Ending Balance	(1,003)	(846)	(1,003)	(846)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(909)	(842)	(970)	(901)
Aggregate adjustment for the period	(92)	(1)	(31)	58
Ending Balance	(1,001)	(843)	(1,001)	(843)
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(23)	(22)	15	(11)
Current period changes in fair value	23	16	(20)	5
Reclassification to income	3	7	7	4
Net tax impact	(3)	(4)	(2)	(1)
Ending Balance	0	(3)	0	(3)
Pension and postretirement plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(1)	0	0	1
Reclassification to income	(2)	(1)	(3)	(2)
Net tax impact	1	1	1	1
Ending Balance	$ (2)	$ 0	$ (2)	$ 0