Employee Benefit Plans - Change in Projected Benefit Obligations and Change in Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Change in Plan Assets:
Fair value of plan assets at beginning of year	$ 300
Fair value of plan assets at end of year	217	$ 300
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	99	157
Service cost		1	$ 1
Interest cost		4	5
(Gain) loss from changes in actuarial assumptions and plan experience	(1)	2
Benefits paid	(3)	(7)
Settlements or curtailments	(92)	(57)
Other		(1)
Benefit obligation at end of year	3	99	157
Change in Plan Assets:
Fair value of plan assets at beginning of year	96	151
Actual return on plan assets	1	9
Employer contribution		1
Benefits paid	(3)	(7)
Settlements or curtailments	(92)	(57)
Expenses paid from assets		(1)
Fair value of plan assets at end of year		96	151
Funded status	(3)	(3)
Recognized asset (liability)	(3)	(3)
Other	(2)
Pension Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	231	220
Service cost	6	5	7
Interest cost	3	3	5
Plan participants’ contribution	1	1
Foreign currency exchange rate changes	6	7
(Gain) loss from changes in actuarial assumptions and plan experience	(11)	5
Benefits paid	(8)	(8)
Settlements or curtailments	(8)	(2)
Other	1
Benefit obligation at end of year	221	231	220
Change in Plan Assets:
Fair value of plan assets at beginning of year	204	195
Actual return on plan assets	14	7
Employer contribution	7	6
Plan participants’ contribution	1	1
Foreign currency exchange rate changes	7	5
Benefits paid	(8)	(8)
Settlements or curtailments	(8)	(2)
Fair value of plan assets at end of year	217	204	195
Funded status	(4)	(27)
Recognized asset (liability)	(4)	(27)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	27	28
Interest cost		1	1
(Gain) loss from changes in actuarial assumptions and plan experience		1
Benefits paid	(2)	(3)
Benefit obligation at end of year	25	27	28
Change in Plan Assets:
Employer contribution	2	3
Benefits paid	(2)	(3)
Funded status	(25)	(27)
Recognized asset (liability)	(25)	(27)
Postretirement Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	20	20
Interest cost	1		1
Foreign currency exchange rate changes	1
(Gain) loss from changes in actuarial assumptions and plan experience	(2)
Benefits paid	(1)
Benefit obligation at end of year	19	20	$ 20
Change in Plan Assets:
Employer contribution	1
Benefits paid	(1)
Funded status	(19)	(20)
Recognized asset (liability)	$ (19)	$ (20)