Restructuring - Additional Information (Detail)			3 Months Ended			6 Months Ended
	Oct. 01, 2019 USD ($)	Oct. 01, 2017 USD ($) ProductionUnit	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring Charges			$ 2,000,000	$ 9,000,000
Proceeds from sale of land								$ 13,000,000
Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Accrued environmental costs			5,000,000				$ 5,000,000
Scenario, Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Accelerated depreciation charges						$ 1,000,000
Scenario, Forecast [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Accelerated depreciation charges	$ 1,000,000
Purification Solutions Transformation Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring Charges							9,000,000
Severance costs			1,000,000				8,000,000
Professional fees							1,000,000
Restructuring cash payments of fiscal year			1,000,000				2,000,000
Accrued severance charges			$ 6,000,000				6,000,000
Purification Solutions Transformation Plan [Member] | Scenario, Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring cash payments through the reminder of fiscal 2019 and thereafter						7,000,000
Marshall, Texas Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring Charges		$ 1,000,000
Number of idled production units | ProductionUnit		3
Number of production units | ProductionUnit		7
Accelerated depreciation charges		$ 1,000,000
Marshall, Texas Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs		$ 1,000,000
Operational Restructuring [Member] | Merak, Indonesia [Member] | Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Proceeds from sale of land					$ 13,000,000
Net benefit to earnings					$ 11,000,000
Operational Restructuring [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring Charges							1,000,000	1,000,000
Previous Actions and Sites Pending Sale [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs							1,000,000	$ 1,000,000
Accelerated depreciation charges							$ 1,000,000
Previous Actions and Sites Pending Sale [Member] | Scenario, Forecast [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring cash payments through the reminder of fiscal 2019 and thereafter						5,000,000
Previous Actions and Sites Pending Sale [Member] | Scenario, Forecast [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Severance charges expected to paid in fiscal 2019						$ 1,000,000