Equity and Noncontrolling Interests - Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance			$ 325
Ending balance	$ 362		362
Redeemable Noncontrolling Interest
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	37	$ 39	47	$ 28
Net income	6	3	24	19
Foreign currency translation adjustments	2	(2)	2	0
Dividends	0	1	(28)	(7)
Change in noncontrolling interest share	0	0	0	1
Ending balance	$ 45	$ 41	$ 45	$ 41