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

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

[2] Included $12 million classified in accounts receivable on the Consolidated Balance Sheets as of September 30, 2022 and 2021.

[3] 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 described in Note A. The total allowance for credit losses was $2 million as of September 30,2022.

[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 described in Note A. The total allowance for credit losses was $1 million as of September 30,2022.