Goodwill and Intangible Assets - Schedule of Changes in Balances (Detail) $ in Millions	9 Months Ended
	Jun. 30, 2024 USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 134
Foreign currency impact	(2)
Ending balance	132
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	51
Foreign currency impact	(2)
Ending balance	49
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	83
Ending balance	$ 83