Other Assets - Summary of Other Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Other Assets, Noncurrent [Abstract]
Investments in non-consolidated joint ventures	$ 116	$ 110
Deferred income tax assets, net	139	122
Prepaid pension costs	161	149
Other	262	225
Other assets	$ 678	$ 606