Cash Flows - Employer Contributions (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits | U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual employer contributions	$ 9	$ 1
Expected employer contributions
Expected employer contributions 2018	1
Expected benefit payments
Expected benefit payments 2018	161
Expected benefit payments 2019	83
Expected benefit payments 2020	82
Expected benefit payments 2021	80
Expected benefit payments 2022	75
Expected benefit payments 2023-2027	323
Pension Benefits | Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual employer contributions	5	102
Expected employer contributions
Expected employer contributions 2018	5
Expected benefit payments
Expected benefit payments 2018	5
Expected benefit payments 2019	5
Expected benefit payments 2020	5
Expected benefit payments 2021	5
Expected benefit payments 2022	5
Expected benefit payments 2023-2027	29
Other Postretirement Benefits | U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual employer contributions	3	$ 3
Expected employer contributions
Expected employer contributions 2018	2
Expected benefit payments
Expected benefit payments 2018	2
Expected benefit payments 2019	2
Expected benefit payments 2020	2
Expected benefit payments 2021	1
Expected benefit payments 2022	1
Expected benefit payments 2023-2027	$ 1