Equity and Noncontrolling Interests - Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	$ 1,842	$ 1,883	$ 1,535	$ 2,189
Aggregate adjustment for the period, net of tax	42	41	96	(88)
Stockholders' equity, ending balance	1,807	1,572	1,807	1,572
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(619)	(690)	(665)	(569)
Stockholders' equity, ending balance	(578)	(658)	(578)	(658)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(605)	(632)	(634)	(558)
Aggregate adjustment for the period, net of tax	24	8	53	(66)
Stockholders' equity, ending balance	(581)	(624)	(581)	(624)
Realized and unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(11)	(55)	(28)	(8)
Current period changes in fair value, net of tax	18	12	33	(30)
Reclassification to income, net of tax	(1)	12	1	7
Stockholders' equity, ending balance	6	(31)	6	(31)
Pension and postretirement plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(3)	(3)	(3)	(3)
Stockholders' equity, ending balance	$ (3)	$ (3)	$ (3)	$ (3)