Restructuring - Additional Information (Detail)			1 Months Ended			3 Months Ended	12 Months Ended			84 Months Ended
	Oct. 20, 2015 Position	Apr. 26, 2013 Employees	Sep. 30, 2016 USD ($)	Nov. 30, 2015 Employees	Jan. 31, 2014 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2013 USD ($)
Restructuring Cost And Reserve [Line Items]
Site demolition, clearing and environmental remediation costs							$ 1,000,000	$ 1,000,000	$ 15,000,000
Restructuring costs in accrued expenses			$ 5,000,000				5,000,000	9,000,000	19,000,000	$ 5,000,000	$ 10,000,000
Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings							1,000,000	13,000,000	8,000,000
Severance charges								7,000,000	3,000,000
Other charges								2,000,000
Accelerated depreciation and asset write-offs								4,000,000	5,000,000
Severance Costs [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges								5,000,000
Severance Costs [Member] | Maximum [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges			1,000,000				1,000,000			1,000,000
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs in accrued expenses			3,000,000				3,000,000	5,000,000	16,000,000	3,000,000	7,000,000
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs in accrued expenses			2,000,000				2,000,000	2,000,000	2,000,000	2,000,000	$ 2,000,000
Operational Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Number of positions eliminated | Position	300
Pre-tax charge to earnings							29,000,000
Additional pre-tax cash charges to earnings							1,000,000
Expected cumulative net cash outlays related to plan			30,000,000				30,000,000			30,000,000
Cash payments							27,000,000
Severance charges							23,000,000
Other charges							4,000,000
Expected severance charges			3,000,000				3,000,000			3,000,000
Operational Restructuring [Member] | Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges			2,000,000				2,000,000			2,000,000
Closure of Carbon Black Facility [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings							25,000,000
Expected cumulative net cash outlays related to plan			5,000,000				5,000,000			5,000,000
Cash payments							2,000,000
Severance charges							2,000,000
Affected employees | Employees				50
Site demolition, clearing and environmental remediation charges, and other miscellaneous costs, thereafter							3,000,000
Site demolition, clearing and environmental remediation costs							3,000,000
Restructuring future cash payments remainder of fiscal 2017							3,000,000
Closure of Carbon Black Facility [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Other charges							1,000,000
Closure of Carbon Black Facility [Member] | Severance Costs [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges			1,000,000				1,000,000			1,000,000
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							22,000,000
Closure of Carbon Black Facility [Member] | Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings							3,000,000
Transition Services Agreement
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings					$ 24,000,000			6,000,000	18,000,000
Cash payments			1,000,000				21,000,000
Severance charges					16,000,000		14,000,000
Other charges					$ 8,000,000		7,000,000
Restructuring costs in accrued expenses			0				0			0
Transition Services Agreement | Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges								2,000,000
Closure of Port Dickson [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings							19,000,000
Severance charges							2,000,000
Other charges							1,000,000
Affected employees | Employees		90
Site demolition, clearing and environmental remediation costs							2,000,000
Pre-tax benefit to earnings							1,000,000
Accelerated depreciation and asset write-offs							16,000,000
Expected cumulative net cash received to this plan			$ 3,000,000				$ 3,000,000			$ 3,000,000
Closure of Port Dickson [Member] | Land [Member]
Restructuring Cost And Reserve [Line Items]
Gain on sale of asset						$ 2,000,000
Closure of Port Dickson [Member] | Cabot [Member]
Restructuring Cost And Reserve [Line Items]
Equity share in CMSB		50.10%
Closure of Port Dickson [Member] | CMSB [Member]
Restructuring Cost And Reserve [Line Items]
Portion of the charges that are allocable to the noncontrolling interest			49.90%				49.90%			49.90%
Closure of Port Dickson [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings								1,000,000	2,000,000
Restructuring costs in accrued expenses			$ 1,000,000				$ 1,000,000	1,000,000		$ 1,000,000
Closure of Port Dickson [Member] | Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan			2,000,000				2,000,000			2,000,000
Closure of Port Dickson [Member] | Asset Sales [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan			7,000,000				7,000,000			7,000,000
Closure of Port Dickson [Member] | Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan			1,000,000				1,000,000			1,000,000
Closure of Port Dickson [Member] | Facility Closure Costs [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan			1,000,000				1,000,000			1,000,000
Previous Actions and Sites Pending Sale [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings								2,000,000	$ 1,000,000
Cash payments										79,000,000
Severance charges							67,000,000			63,000,000
Other charges							23,000,000			25,000,000
Expected severance charges			158,000,000				158,000,000			158,000,000
Site demolition, clearing and environmental remediation costs							10,000,000			10,000,000
Gain on sale of asset							8,000,000
Restructuring accelerated depreciation and asset impairments							66,000,000
Proceeds from sale of Assets										19,000,000
Previous Actions and Sites Pending Sale [Member] | Land [Member]
Restructuring Cost And Reserve [Line Items]
Net pre-tax gain							7,000,000
Previous Actions and Sites Pending Sale [Member] | Severance Costs [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges			$ 2,000,000				2,000,000	$ 2,000,000		$ 2,000,000
Previous Actions and Sites Pending Sale [Member] | Environmental and Other Closure Related Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring cash payments through the reminder of fiscal 2017 and thereafter							$ 2,000,000