Debt - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Interest expense, net	$ 42	$ 43	$ 43	$ 45	$ 45	$ 45	$ 45	$ 46	$ 173	$ 181	$ 203
Weighted-average interest rate of total debt	5.30%				5.60%				5.30%	5.60%	5.60%
Senior Notes
Debt Instrument [Line Items]
Scheduled maturities of long-term debt in 2019	$ 627								$ 627
Scheduled to mature	$ 1,210								$ 1,210
Revolving Credit Facility
Debt Instrument [Line Items]
Extended maturity date of credit facility									Apr. 01, 2021
Term Loan Facility
Debt Instrument [Line Items]
Credit Facility maturity date									Jul. 01, 2020
Extended maturity date of credit facility									Nov. 01, 2023