Restructuring - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended			12 Months Ended
	Oct. 31, 2015 Employees	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)
Restructuring Cost And Reserve [Line Items]
Cash payments		$ 2			$ 3
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Cash payments		1			2
Operational Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Number of employees termination | Employees	300
Restructuring expected charges		30			30
Pre-tax charge to earnings			$ 2		1	$ 26	$ 29
Expected cumulative net cash outlays related to plan		30			30
Cash payments					29		27
Restructuring cash payments through the reminder of fiscal 2017					1
Operational Restructuring [Member] | Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges		1			1
Operational Restructuring [Member] | Maximum [Member] | Scenario, Forecast
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings				$ 1
Closure of Carbon Black Facility [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expected charges		27			27
Pre-tax charge to earnings						25	$ 25
Expected cumulative net cash outlays related to plan		6			6
Cash payments					3
Restructuring cash payments through the reminder of fiscal 2017					3
Site demolition, clearing and environmental remediation charges, and other miscellaneous costs remainder of fiscal year 2017					2
Site demolition, clearing and environmental remediation charges, and other miscellaneous costs, thereafter					2
Site demolition, clearing and environmental remediation costs					3
Severance charges					3
Restructuring cash payments, thereafter					3
Closure of Carbon Black Facility [Member] | Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges		1			1
Closure of Carbon Black Facility [Member] | Non-Cash Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						23
Closure of Carbon Black Facility [Member] | Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						2
Closure of Carbon Black Facility [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings		1	1		1
Previous Actions and Sites Pending Sale [Member]
Restructuring Cost And Reserve [Line Items]
Severance charges		1
Net benefit to earnings			$ 8			$ 8
Previous Actions and Sites Pending Sale [Member] | Severance Costs [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges		2			2
Restructuring cash payments through the reminder of fiscal 2017 and thereafter					3
Previous Actions and Sites Pending Sale [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings		$ 1			$ 1