Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 814	$ 1,134
Ending Balance	1,090	814
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(307)	(338)
Other comprehensive income (loss) before reclassifications	52	42
Amounts reclassified from AOCI	(3)	(3)
Adoption of accounting standards		(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests	7	5
Ending Balance	(265)	(307)
Unrealized Gains on Investment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		1
Adoption of accounting standards		(1)
Pension and Other Postretirement Benefit Liability Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(44)	(54)
Other comprehensive income (loss) before reclassifications	20	3
Amounts reclassified from AOCI		6
Adoption of accounting standards		1
Ending Balance	(24)	(44)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(351)	(391)
Other comprehensive income (loss) before reclassifications	72	45
Amounts reclassified from AOCI	(3)	3
Adoption of accounting standards		(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests	7	5
Ending Balance	$ (289)	$ (351)