Litigation, Claims and Contingencies - Schedule of Progression of Activity in the Asbestos Reserve (Details) - USD ($) $ in Millions		6 Months Ended				12 Months Ended
		Mar. 31, 2023		Mar. 31, 2022		Sep. 30, 2022		Sep. 30, 2021		Sep. 30, 2020
Ashland [Member]
Asbestos reserve [Roll Forward]
Asbestos reserve - beginning of year		$ 305	[1]	$ 320	[1]	$ 320	[1]	$ 335	[1]	$ 352
Reserve adjustment		0		0		16		12		13
Amounts paid		(20)		(19)		(31)		(27)		(30)
Asbestos reserve - end of period	[1]	285		301		305		320		335
Hercules [Member]
Asbestos reserve [Roll Forward]
Asbestos reserve - beginning of year		213	[2]	217	[2]	217	[2]	229	[2]	252
Reserve adjustment		0		0		15		8		(3)
Amounts paid		(8)		(10)		(19)		(20)		(20)
Asbestos reserve - end of period	[2]	$ 205		$ 207		$ 213		$ 217		$ 229

[1] Included $29 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets as of March 31, 2023 and September 30, 2022.

[2] Included $18 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets as of March 31, 2023 and September 30, 2022.