Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 1,279	$ 1,625	$ 1,389
Ending Balance	1,134	1,279	1,625
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(266)	(204)
Other comprehensive income (loss) before reclassifications	(69)	(64)
Amounts reclassified from AOCI	(9)	(2)
Less: Other comprehensive income (loss) attributable to noncontrolling interests	(6)	(4)
Ending Balance	(338)	(266)	(204)
Unrealized Gains on Investment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	1	2
Other comprehensive income (loss) before reclassifications		(1)
Ending Balance	1	1	2
Pension and Other Postretirement Benefit Liability Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(52)	(57)
Other comprehensive income (loss) before reclassifications	4	6
Amounts reclassified from AOCI	(6)	(1)
Ending Balance	(54)	(52)	(57)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(317)	(259)	(325)
Other comprehensive income (loss) before reclassifications	(65)	(59)
Amounts reclassified from AOCI	(15)	(3)	2
Less: Other comprehensive income (loss) attributable to noncontrolling interests	(6)	(4)
Ending Balance	$ (391)	$ (317)	$ (259)