Litigation, Claims and Contingencies - Summary of Progression of Insurance Receivable (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended				12 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022		Jun. 30, 2021		Sep. 30, 2021		Sep. 30, 2020		Sep. 30, 2019
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance settlement		$ 2	$ 0	$ 5		$ 1
Ashland [Member]
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable - beginning of year				100	[1]	103	[1]	$ 103	[1]	$ 123	[1]	$ 140
Receivable adjustment	[2]			7		6		6		1		(5)
Insurance settlement				0		0		0		(10)		0
Amounts collected				(5)		(7)		(9)		(11)		(12)
Insurance receivable - end of period	[1]	102	102	102		102		100		103		123
Hercules [Member]
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Insurance receivable - beginning of year				47	[3]	47	[3]	47	[3]	49	[3]	54
Receivable adjustment	[4]			7		1		1		(2)		(5)
Amounts collected				(1)		0		(1)		0		0
Insurance receivable - end of period	[3]	$ 53	$ 48	$ 53		$ 48		$ 47		$ 47		$ 49

[1] Includes $12 million classified in accounts receivable on the Condensed Consolidated Balance Sheets as of June 30, 2022 and September 30, 2021.

[2] The nine months ended June 30, 2021 includes a reserve adjustment of $2 million 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 June 30, 2022.

[3] Includes $3 million and $1 million classified in accounts receivable on the Condensed Consolidated Balance Sheets as of June 30, 2022 and September 30, 2021, respectively.

[4] The nine months ended June 30, 2021 includes a reserve adjustment of $1 million 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 June 30, 2022.