Employee Benefit Plans - Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 1	$ 1	$ 1
Interest cost	1	1	4	3
Expected return on plan assets	(2)	(3)	(7)	(8)
Net periodic benefit (credit) cost		(1)	(2)	(4)
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	5	6
Interest cost	1	2	4	6
Expected return on plan assets	(2)	(4)	(8)	(11)
Amortization of prior service cost (credit)	2		2
Amortization of actuarial loss	1	1	2	2
Settlement and curtailment gain			(6)
Net periodic benefit (credit) cost	4	1	(1)	3
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		1	1	1
Amortization of prior service cost (credit)		$ (1)	(1)	(2)
Amortization of actuarial loss	(1)		(1)
Net periodic benefit (credit) cost	$ (1)		$ (1)	$ (1)