Goodwill and Intangible Assets - Schedule of Goodwill Balances (Parenthetical) (Detail) - USD ($)	Sep. 30, 2020	Sep. 30, 2019
Purification Solutions [Member]
Goodwill And Intangible Assets [Line Items]
Accumulated impairment losses	$ 444,000,000	$ 444,000,000
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Accumulated impairment losses	0	0
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Accumulated impairment losses	$ 0	$ 0