Litigation, Claims and Contingencies - Summary of Progression of Insurance Receivable (Parenthetical) (Details) - Ashland [Member] - USD ($) $ in Millions	Dec. 31, 2018		Sep. 30, 2018		Dec. 31, 2017	[1]	Sep. 30, 2017	[1]	Sep. 30, 2016	[1]	Sep. 30, 2015
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable	$ 139	[1]	$ 140	[1]	$ 151		$ 155		$ 151		$ 150
Accounts Receivable [Member]
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable	$ 15		$ 15

[1] Included $15 million classified in accounts receivable on the Condensed Consolidated Balance Sheets as of both December 31, 2018 and September 30, 2018