Restructuring - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended				12 Months Ended
	Sep. 30, 2014	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2015	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Proceeds from the sale of land								$ 39
Purification Solutions Transformation Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring Charges							$ 9
Professional fees and other charges							1
Restructuring cash payments of fiscal year							8
Accrued severance charges							1
Purification Solutions Transformation Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs							$ 8
Purification Solutions Transformation Plan [Member] | Scenario, Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges expected in fiscal year						$ 1
Restructuring cash payments in fiscal 2020						$ 2
Operational Restructuring [Member] | Thane, India [Member]
Restructuring Cost And Reserve [Line Items]
Proceeds from the sale of land		$ 28						28
Net benefit to earnings								$ 28
Refundable cash deposit	$ 22		$ 3		$ 3
Operational Restructuring [Member] | Merak, Indonesia [Member] | Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Proceeds from the sale of land				$ 13
Net benefit to earnings				$ 11