Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	8	8	24	24
Expected return on plan assets	(17)	(17)	(53)	(52)
Settlement loss	2	3	2	3
Total net periodic benefit cost (income)	(7)	(6)	(27)	(25)
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	3	3
Interest cost	3	3	10	9
Expected return on plan assets	(5)	(5)	(14)	(15)
Settlement loss	0	0	0	0
Total net periodic benefit cost (income)	$ (1)	$ (1)	$ (1)	$ (3)