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