Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions		12 Months Ended
	Oct. 01, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 1,134	$ 1,134	$ 1,279	$ 1,625
Adoption of accounting standards	2
Ending Balance		814	1,134	1,279
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(338)	(338)	(266)
Other comprehensive income (loss) before reclassifications		42	(69)
Amounts reclassified from AOCI		(3)	(9)
Adoption of accounting standards		(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		5	(6)
Ending Balance		(307)	(338)	(266)
Unrealized Gains on Investment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	1	1	1
Adoption of accounting standards		(1)
Ending Balance			1	1
Pension and Other Postretirement Benefit Liability Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(54)	(54)	(52)
Other comprehensive income (loss) before reclassifications		3	4
Amounts reclassified from AOCI		6	(6)
Adoption of accounting standards		1
Ending Balance		(44)	(54)	(52)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (391)	(391)	(317)	(259)
Other comprehensive income (loss) before reclassifications		45	(65)
Amounts reclassified from AOCI		3	(15)	(3)
Adoption of accounting standards		(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		5	(6)
Ending Balance		$ (351)	$ (391)	$ (317)