Components of Net Periodic Benefit Cost (Detail) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	8	8	16	16
Expected return on plan assets	(18)	(18)	(36)	(35)
Total net periodic benefit cost (income)	(10)	(10)	(20)	(19)
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2	2
Interest cost	4	3	7	6
Expected return on plan assets	(5)	(5)	(9)	(10)
Total net periodic benefit cost (income)	$ 0	$ (1)	$ 0	$ (2)