Employee Benefit Plans - Net Periodic Defined Benefit Pension Costs (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge		$ 6	$ 3
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost				$ 1		$ 1
Interest cost				1		2
Expected return on plan assets				(1)		(2)
Settlement charge					$ 6
Net periodic benefit (credit) cost				1	6	1
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2			2	3	3
Interest cost	1			1	2	2
Expected return on plan assets	$ (3)			$ (3)	(5)	(5)
Amortization of actuarial loss					1	1
Net periodic benefit (credit) cost					$ 1	$ 1