Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2017 USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 154
Goodwill acquired	31	[1]
Foreign currency impact	(1)
Ending balance	184
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	53
Foreign currency impact	(2)
Ending balance	51
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	9
Goodwill acquired	31	[1]
Foreign currency impact	1
Ending balance	41
Purification Solutions [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	92
Ending balance	$ 92

[1] Consists of goodwill acquired in the acquisition of Tech Blend as described in Note C.