Litigation, Claims and Contingencies - Summary of Progression of Insurance Receivable (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended				12 Months Ended
		Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023		Mar. 31, 2022		Sep. 30, 2022		Sep. 30, 2021		Sep. 30, 2020
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance settlement		$ (0)	$ 3	$ (0)		$ 3
Ashland [Member]
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable - beginning of year				101	[1]	100	[1]	$ 100	[1]	$ 103	[1]	$ 123
Receivable adjustment	[2]			0		0		7		6		1
Insurance settlement				0		0		0		0		(10)
Amounts collected				(5)		(2)		(6)		(9)		(11)
Insurance receivable - end of period	[1]	96	98	96		98		101		100		103
Hercules [Member]
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable - beginning of year				52	[3]	47	[3]	47	[3]	47	[3]	49
Receivable adjustment	[4]			0		0		7		1		(2)
Amounts collected				(1)		(1)		(2)		(1)		0
Insurance receivable - end of period	[3]	$ 51	$ 46	$ 51		$ 46		$ 52		$ 47		$ 47

[1] Includes $12 million classified in accounts receivable on the Condensed Consolidated Balance Sheets as of March 31, 2023 and September 30, 2022.

[2] 2021 includes a $2 million reserve adjustment related to allowances for credit losses as a result of Ashland's adoption of the new credit measurement standard. The total allowance for credit losses was $2 million as of March 31, 2023 and September 30, 2022.

[3] Includes $2 million and $3 million classified in accounts receivable on the Condensed Consolidated Balance Sheets as of March 31, 2023 and September 30, 2022, respectively.

[4] 2021 includes a $1 million reserve adjustment related to allowances for credit losses as a result of Ashland's adoption of the new credit measurement standard. The total allowance for credit losses was $1 million as of March 31, 2023 and September 30, 2022.