Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2021 USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 134	[1]
Foreign currency impact	6	[1]
Ending balance	140	[1]
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	46
Foreign currency impact	2
Ending balance	48
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	88
Foreign currency impact	4
Ending balance	$ 92

[1] The balance as of September 30, 2020 and September 30, 2021 includes $444 million of accumulated impairment losses associated with the goodwill of Purification Solutions segment. There were no accumulated impairment losses associated with the goodwill of the Reinforcement Materials or Performance Chemicals segments.