Derivative Financial Instruments - Summary of Amounts Recorded in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Sep. 30, 2018
Other Current Assets
Derivatives Fair Value [Line Items]
Other assets	[1],[2]	$ 2
Other Noncurrent Assets
Derivatives Fair Value [Line Items]
Other assets	[3]		$ 4
Other Noncurrent Liabilities
Derivatives Fair Value [Line Items]
Other liabilities	[1]	$ 5

[1] $6 million and $4 million of foreign exchange derivative contracts in asset and liability positions, respectively, and $5 million of interest rate swap in a liability 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] $4 million of interest rate swap in an asset position.