Derivative Instruments and Hedging Activities - Gains (Losses) on Net Investment Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) recorded to Accumulated other comprehensive income (loss), net of tax	$ 46	$ 40
Foreign currency-denominated debt
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) recorded to Accumulated other comprehensive income (loss), net of tax	145	(29)
Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) recorded to Accumulated other comprehensive income (loss), net of tax	67	$ (55)
Terminated Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) recorded to Accumulated other comprehensive income (loss), net of tax	$ (18)