Fair Value Measurements - Schedule of Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions		Jun. 30, 2018	Sep. 30, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contractual Obligations			$ (5)
Total		$ (2)
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total		4
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contractual Obligations			(5)
Total		(6)
Other Current Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign Currency Forward Exchange Contracts	[1],[2]	3
Other Current Assets | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign Currency Forward Exchange Contracts	[2]	3
Other Current Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign Currency Forward Exchange Contracts	[1],[2]	(1)
Other Current Liabilities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign Currency Forward Exchange Contracts	[2]	(1)
Other Noncurrent Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign Currency Forward Exchange Contracts	[1]	2
Interest rate swap	[3]	2
Other Noncurrent Assets | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Interest rate swap	[3]	2
Other Noncurrent Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contractual Obligations	[3]	(6)	(5)
Other Noncurrent Liabilities | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contractual Obligations	[3]	$ (6)	$ (5)

[1] $5 million and $3 million of foreign exchange derivative contracts in asset and liability positions, respectively, and $2 million of interest rate swap in an asset position including non-designated cash flow hedges.

[2] The fair value of foreign currency forward exchange contracts is based on dealer quotes of market forward rates and reflects the amount that the Company would receive or pay at their maturity dates for contracts involving the same currencies and maturity dates.

[3] The fair value of the interest rate swap is based on dealer quotes of market forward rates and reflects the amount that the Company would receive or pay as of June 30, 2018 for contracts involving the same attributes and maturity dates.