Employee Benefit Plans - Change in Projected Benefit Obligations and Change in Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Change in Benefit Obligations:
Settlements or curtailments			$ (17)
Change in Plan Assets:
Fair value of plan assets at beginning of year	$ 462
Fair value of plan assets at end of year	474	$ 462
U.S. Pension Benefits [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	175	170
Service cost	1	1	1
Interest cost	4	4	7
(Gain) Loss from changes in actuarial assumptions and plan experience	(7)	14
Benefits paid	(7)	(7)
Settlements or curtailments	(5)	(6)
Other	(1)	(1)
Benefit obligation at end of year	160	175	170
Change in Plan Assets:
Fair value of plan assets at beginning of year	157	153
Service cost	1	1	1
Interest cost	4	4	7
Actual return on plan assets	12	18
Employer contribution	1
(Gain) Loss from changes in actuarial assumptions and plan experience	(7)	14
Benefits paid	(7)	(7)
Settlements	(6)	(6)
Expenses paid from assets	(1)	(1)
Fair value of plan assets at end of year	156	157	153
Funded status	(4)	(18)
Recognized liability	(4)	(18)
Foreign Pension Benefits [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	400	348
Service cost	10	8	9
Interest cost	6	8	11
Plan participants’ contribution	2	2
Foreign currency exchange rate changes	16	(9)
(Gain) Loss from changes in actuarial assumptions and plan experience	(42)	62
Benefits paid	(12)	(14)
Settlements or curtailments	(3)	(4)
Other	(1)	(1)
Benefit obligation at end of year	376	400	348
Change in Plan Assets:
Fair value of plan assets at beginning of year	305	279
Service cost	10	8	9
Interest cost	6	8	11
Plan participants’ contribution	2	2
Actual return on plan assets	6	43
Employer contribution	9	10
Plan participants’ contribution	2	2
Foreign currency exchange rate changes	12	(11)
(Gain) Loss from changes in actuarial assumptions and plan experience	(42)	62
Benefits paid	(12)	(14)
Settlements	(3)	(3)
Expenses paid from assets	(1)	(1)
Fair value of plan assets at end of year	318	305	279
Funded status	(58)	(95)
Recognized liability	(58)	(95)
U. S. Postretirement Benefits [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	37	38
Interest cost	1	1	2
(Gain) Loss from changes in actuarial assumptions and plan experience	(2)	1
Benefits paid	(3)	(3)
Benefit obligation at end of year	33	37	38
Change in Plan Assets:
Interest cost	1	1	2
Employer contribution	3	3
(Gain) Loss from changes in actuarial assumptions and plan experience	(2)	1
Benefits paid	(3)	(3)
Funded status	(33)	(37)
Recognized liability	(33)	(37)
Foreign Postretirement Benefits [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	20	15
Interest cost	1	1	1
Foreign currency exchange rate changes		(1)
(Gain) Loss from changes in actuarial assumptions and plan experience	(1)	5
Benefits paid		(1)
Benefit obligation at end of year	20	20	15
Change in Plan Assets:
Interest cost	1	1	$ 1
Employer contribution		1
(Gain) Loss from changes in actuarial assumptions and plan experience	(1)	5
Benefits paid		(1)
Funded status	(20)	(20)
Recognized liability	$ (20)	$ (20)