Equity and Noncontrolling Interests - Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' equity attributable to noncontrolling interest	$ 322
Dividends	(42)	$ (54)	$ (61)
Stockholders' equity attributable to noncontrolling interest	342	322
Redeemable noncontrolling interest
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' equity attributable to noncontrolling interest	43	51	47
Net income attributable to the entity	25	19	30
Foreign currency translation adjustments	(8)	(4)	3
Dividends	(14)	(23)	(29)
Business acquisition	194	0	0
Stockholders' equity attributable to noncontrolling interest	$ 240	$ 43	$ 51