Litigation, Claims and Contingencies - Schedule of Progression of Activity in the Asbestos Reserve (Parenthetical) (Details) - USD ($) $ in Millions	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2018	Sep. 30, 2017
Ashland [Member]
Asbestos reserve [Roll Forward]
Asbestos reserve	$ 335	[1]	$ 352	[1]	$ 380	$ 419
Ashland [Member] | Other Current Liabilities [Member]
Asbestos reserve [Roll Forward]
Asbestos reserve	29		28
Hercules [Member]
Asbestos reserve [Roll Forward]
Asbestos reserve	229	[2]	252	[2]	$ 282	$ 323
Hercules [Member] | Other Current Liabilities [Member]
Asbestos reserve [Roll Forward]
Asbestos reserve	$ 22		$ 21

[1] Included $29 million and $28 million classified in accrued expenses and other liabilities on the Consolidated Balance Sheets as of September 30, 2020 and 2019, respectively.

[2] Included $22 million and $21 million classified in accrued expenses and other liabilities on the Consolidated Balance Sheets as of September 30, 2020 and 2019, respectively.