Equity and Noncontrolling Interests - Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period			$ 2,717
Balance at end of period	$ 2,281	$ 4,153	2,281	$ 4,153
Accumulated other comprehensive income (loss), end of period
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(479)	(185)	(531)	(397)
Balance at end of period	(499)	(447)	(499)	(447)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(472)	(195)	(523)	(398)
Aggregate adjustment for the period, net of tax	(25)	(235)	26	(32)
Balance at end of period	(497)	(430)	(497)	(430)
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(6)	3	(7)	3
Current period changes in fair value, net of tax	5	(20)	6	(18)
Reclassification to income, net of tax	0	2	0	0
Balance at end of period	(1)	(15)	(1)	(15)
Pension and postretirement plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(1)	7	(1)	(2)
Net reclassifications to AOCI	0	(9)	0	0
Balance at end of period	$ (1)	$ (2)	$ (1)	$ (2)