Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	6 Months Ended
Mar. 31, 2019 USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 93
Foreign currency impact	(2)
Ending balance	91
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	52
Foreign currency impact	(1)
Ending balance	51
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	41
Foreign currency impact	(1)
Ending balance	$ 40

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant