Employee Benefit Plans - Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
U.S. Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 1	$ 1
Interest cost	4	4	7
Expected return on plan assets	(9)	(10)	(11)
Net periodic (benefit) cost	(4)	(5)	(3)
Foreign Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	8	9
Interest cost	6	8	11
Expected return on plan assets	(14)	(14)	(14)
Amortization of prior service cost			3
Net losses	5	3	4
Settlements or Curtailments cost		1	18
Net periodic (benefit) cost	7	6	31
U. S. Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	2
Amortization of prior service cost	(3)	(3)	(4)
Settlements or Curtailments cost		(1)
Net periodic (benefit) cost	(2)	(3)	(2)
Foreign Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	1
Net periodic (benefit) cost	$ 1	$ 1	$ 1