Income Taxes - Summary of Income from Continuing Operations Before Income Taxes and Reconciliation of Provision for Income Taxes (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020		Sep. 30, 2019
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
United States		$ (96)	$ (642)		$ (143)
Foreign		231	65		134
Income (loss) from continuing operations before income taxes		135	(577)		(9)
Income taxes computed at U.S. statutory rate	[1]	28	(121)		(2)
Tax reform		(0)	(23)	[2]	29	[2]
Uncertain tax positions		(49)	9		10
Deemed inclusions, foreign dividends and other restructuring	[3]	25	35		31
Foreign tax credits		(20)	(14)		(15)
Valuation allowance changes	[4]	4	(1)		14
Research and development credits		(3)	(6)		(5)
State taxes		(5)	(4)		(8)
Goodwill impairment		2	95		0
International rate differential		(18)	(2)		(30)
Other items	[5]	(2)	10		6
Income tax expense (benefit)		$ (38)	$ (22)		$ 30

[1] The domestic tax rate is 21% for 2021, 2020 and 2019.

[2] 2020 includes a benefit of $23 million from Swiss tax reform. 2019 includes an expense of $29 million related to a return to provision adjustment for transition tax.

[3] 2021 includes $17 million primarily related to GILTI permanent adjustments. 2020 includes $33 million primarily related to GILTI permanent adjustments. 2019 includes $20 million primarily related to GILTI permanent adjustments.

[4] 2021 includes $13 million related to certain foreign tax credits partially offset by $5 million related to state NOL's and $4 million related to foreign jurisdictions. 2019 includes $5 million related to state tax NOL’s and $9 million related to a foreign jurisdiction.

[5] 2021 includes $14 million related to the sale of a Specialty Additives facility partially offset by miscellaneous other items. 2020 includes $4 million for foreign withholding taxes.