Accounts Payable, Accrued Liabilities and Other Liabilities - Components of Other Long-Term Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Payables And Accruals [Abstract]
Employee benefit plan liabilities	$ 118	$ 122
Non-current tax liabilities	19	19
Other accrued liabilities	115	104
Total	$ 252	$ 245