Litigation, Claims and Contingencies - Summary of Progression of Insurance Receivable (Parenthetical) (Details) - Ashland [Member] - USD ($) $ in Millions	Mar. 31, 2020		Sep. 30, 2019		Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable	$ 109	[1]	$ 123	[1]	$ 136	$ 140	$ 155	$ 151
Accounts Receivable [Member]
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable	$ 13		$ 15

[1] Included $13 million and $15 million classified in accounts receivable on the Condensed Consolidated Balance Sheets as of March 31, 2020 and September 30, 2019, respectively