Employee Benefit Plans - Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 1	$ 1
Interest cost		4	5
Expected return on plan assets		(3)	(9)
Settlements or curtailments cost	$ 4	3
Net periodic (benefit) cost	4	5	(3)
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5	7
Interest cost	3	3	5
Expected return on plan assets	(10)	(9)	(10)
Amortization of prior service cost			2
Amortization of net losses	3	3	2
Settlements or curtailments cost	1	1	(7)
Other	2
Net periodic (benefit) cost	5	3	(1)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		1	1
Amortization of prior service cost			(2)
Amortization of net losses		(1)	(1)
Net periodic (benefit) cost			(2)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1		1
Amortization of net losses		1
Net periodic (benefit) cost	$ 1	$ 1	$ 1