Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 154
Foreign currency impact	(2)
Ending balance	152
Accumulated impairment losses	(352)	$ (352)
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	55
Foreign currency impact	(3)
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	90
Foreign currency impact	1
Ending balance	91
Accumulated impairment losses	$ (352)	$ (352)