Employee Benefit Plans - Change in Projected Benefit Obligations and Change in Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Change in Plan Assets:
Fair value of plan assets at beginning of year	$ 474
Fair value of plan assets at end of year	472	$ 474
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	160	175
Service cost	1	1	$ 1
Interest cost	5	4	4
(Gain) Loss from changes in actuarial assumptions and plan experience	(10)	(7)
Benefits paid	(7)	(7)
Settlements or curtailments	(5)	(5)
Other	(1)	(1)
Benefit obligation at end of year	143	160	175
Change in Plan Assets:
Fair value of plan assets at beginning of year	156	157
Actual return on plan assets	4	12
Employer contribution	1	1
Benefits paid	(7)	(7)
Settlements	(4)	(6)
Expenses paid from assets	(1)	(1)
Fair value of plan assets at end of year	149	156	157
Funded status	6	(4)
Recognized asset (liability)	6	(4)
Pension Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	376	400
Service cost	9	10	8
Interest cost	7	6	8
Plan participants’ contribution	2	2
Foreign currency exchange rate changes	(7)	16
(Gain) Loss from changes in actuarial assumptions and plan experience	2	(42)
Benefits paid	(13)	(12)
Settlements or curtailments	(2)	(3)
Other	(1)	(1)
Benefit obligation at end of year	373	376	400
Change in Plan Assets:
Fair value of plan assets at beginning of year	318	305
Actual return on plan assets	17	6
Employer contribution	9	9
Plan participants’ contribution	2	2
Foreign currency exchange rate changes	(7)	12
Benefits paid	(13)	(12)
Settlements	(2)	(3)
Expenses paid from assets	(1)	(1)
Fair value of plan assets at end of year	323	318	305
Funded status	(50)	(58)
Recognized asset (liability)	(50)	(58)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	33	37
Interest cost	1	1	1
(Gain) Loss from changes in actuarial assumptions and plan experience	(2)	(2)
Benefits paid	(3)	(3)
Benefit obligation at end of year	29	33	37
Change in Plan Assets:
Employer contribution	3	3
Benefits paid	(3)	(3)
Funded status	(29)	(33)
Recognized asset (liability)	(29)	(33)
Postretirement Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	20	20
Interest cost	1	1	1
Foreign currency exchange rate changes	(1)
(Gain) Loss from changes in actuarial assumptions and plan experience		(1)
Benefits paid	(1)
Benefit obligation at end of year	19	20	20
Change in Plan Assets:
Employer contribution	1
Benefits paid	(1)
Funded status		(20)	$ (19)
Recognized asset (liability)	$ (19)	$ (20)