Restructuring - Additional Information (Detail) $ in Millions			1 Months Ended	3 Months Ended				9 Months Ended	12 Months Ended
	Sep. 14, 2018 USD ($)	Oct. 01, 2017 USD ($) ProductionUnit Employees	Oct. 31, 2015 Employees	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Restructuring Cost And Reserve [Line Items]
Proceeds from sale of land										$ 39		$ 16
Pre-tax charge to earnings											$ 25	29
Maximum [Member] | Scenario, Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings									$ 1
Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expected charges						$ 3
Severance Costs [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance and other charges				$ 1						1
Merak, Indonesia [Member] | Non-Cash Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expected charges												$ 22
Operational Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Number of employees termination | Employees			300
Pre-tax charge to earnings										1	1
Operational Restructuring [Member] | Thane, India [Member]
Restructuring Cost And Reserve [Line Items]
Proceeds from 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 sale of land						13
Net benefit to earnings						$ 11
Operational Restructuring [Member] | Merak, Indonesia [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings										1	$ 1
Marshall, Texas Plan [Member]
Restructuring Cost And Reserve [Line Items]
Number of idled production units | ProductionUnit		3
Number of production units | ProductionUnit		7
Number of employees termination | Employees		40
Restructuring expected charges		$ 1
Marshall, Texas Plan [Member] | Severance Costs [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expected charges		1
Marshall, Texas Plan [Member] | Non-Cash Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expected charges		$ 1
Closure of Carbon Black Facility [Member] | Merak, Indonesia [Member] | Severance Costs [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance costs				$ 1						1
Previous Actions and Sites Pending Sale [Member]
Restructuring Cost And Reserve [Line Items]
Severance charges										1
Previous Actions and Sites Pending Sale [Member] | Port Dickson and Malaysia [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings										$ 3
Previous Actions and Sites Pending Sale [Member] | Berre and Port Dickson Sites [Member]
Restructuring Cost And Reserve [Line Items]
Accrued environmental costs									$ 4