Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 947	$ 962	$ 814	$ 1,035	$ 814	$ 1,134
Ending Balance	1,094	947	962	1,043	1,094	1,043
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(296)	(221)	(307)		(307)
Other comprehensive income (loss) before reclassifications	71	(76)	94
Amounts reclassified from AOCI	(1)	(1)	(1)
Less: Other comprehensive income (loss) attributable to noncontrolling interests	3	(2)	7
Ending Balance	(229)	(296)	(221)		(229)
Pension and Other Postretirement Benefit Liability Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(40)	(41)	(44)		(44)
Other comprehensive income (loss) before reclassifications	(3)	1	(1)
Amounts reclassified from AOCI	5		4
Ending Balance	(38)	(40)	(41)		(38)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(336)	(262)	(351)	(429)	(351)	(391)
Other comprehensive income (loss) before reclassifications	68	(75)	93
Amounts reclassified from AOCI	4	(1)	3	1	6	1
Less: Other comprehensive income (loss) attributable to noncontrolling interests	3	(2)	7
Ending Balance	$ (267)	$ (336)	$ (262)	$ (400)	$ (267)	$ (400)