Restructuring - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost And Reserve [Line Items]
Restructuring Charges	$ 11	$ 19	$ 16
Reorganization Actions [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs	22	17
Restructuring charges expected in fiscal 2022 related to site demolition and clearing costs	3
Restructuring charges expected thereafter fiscal year related to site demolition and clearing costs	2
Restructuring cash payments of fiscal year	18	13
Restructuring cash payments in fiscal 2022	7
Restructuring future cash payments thereafter fiscal year	2
Accrued severance charges	4
Purification Solutions Transformation Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring cash payments of fiscal year	12	10
Restructuring cash payments in fiscal 2022	2
Restructuring future cash payments thereafter fiscal year	1
Accrued severance charges	1
Restructuring Charges	15	$ 11
Purification Solutions Transformation Plan [Member] | Manufacturing Facility [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges expected in fiscal 2022 related to site demolition and clearing costs	2
Restructuring charges expected thereafter fiscal 2022 related to site demolition and clearing costs	$ 2