Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 17,694
Aggregate adjustment for the period	19	$ 72
Ending Balance	17,874	17,243
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(955)	(911)
Ending Balance	(933)	(864)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(970)	(901)
Aggregate adjustment for the period	61	59
Ending Balance	(909)	(842)
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	15	(11)
Current period changes in fair value	(43)	(11)
Reclassification to income	4	(3)
Net tax impact	1	3
Ending Balance	(23)	(22)
Pension and postretirement plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0	1
Reclassification to income	(1)	(1)
Ending Balance	$ (1)	$ 0