Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	6 Months Ended
	Mar. 31, 2017 USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 152
Foreign currency impact	(1)
Ending balance	151
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	52
Ending balance	52
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	9
Ending balance	9
Purification Solutions [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	91
Foreign currency impact	(1)
Ending balance	$ 90