Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 153		$ 154
Amortization expense estimated for year one	9
Amortization expense estimated for year two	9
Amortization expense estimated for year three	9
Amortization expense estimated for year four	9
Amortization expense estimated for year five	9
Cost of Sales and Selling and Administrative Expenses [Member]
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets	$ 2	$ 4
Minimum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	14 years
Maximum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	25 years
Weighted Average [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	19 years