Derivative Instruments and Hedging Activities Disclosure - Gains (Losses) on Net Investment Hedges (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Forward exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Net Investment Hedge, Gain (Loss), before Reclassification and Tax	$ (106)	$ 138	$ 81
Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Net Investment Hedge, Gain (Loss), before Reclassification and Tax	(109)	73	0
Foreign Exchange Forward
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Net Investment Hedge, Gain (Loss), before Reclassification and Tax	$ 0	$ (9)	$ 0