Comprehensive (Loss) Income - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		$ 308	$ 210	$ 239
Ending balance		(320)	308	210
Foreign Currency Translation Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		(171)	(201)	(157)
Other comprehensive (loss) income	[1]	(13)	30	(44)
Ending balance		(184)	(171)	(201)
Minimum Pension Liability Adjustment
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		(10)	(17)	(10)
Other comprehensive (loss) income	[1]	1	8	(6)
Amounts reclassified from accumulated other comprehensive income			(1)	(1)
Ending balance		(9)	(10)	(17)
Deferred Gains On Derivative Financial Instruments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income	[1]	3
Ending balance		3
Accumulated Other Comprehensive Loss, net
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		(181)	(218)	(167)
Other comprehensive (loss) income	[1]	(9)	38	(50)
Amounts reclassified from accumulated other comprehensive income			(1)	(1)
Ending balance		$ (190)	$ (181)	$ (218)

[1] Includes historical foreign currency translation related to certain intra-entity transactions that are no longer of a long-term investment nature of $0 million, $(19) million and $(109) million during the fiscal year ended September 30, 2018, 2017 and 2016, respectively.