Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 28, 2016
Deferred tax assets
Non-U.S. net operating loss carryforwards	$ 2	$ 2
State net operating loss carryforwards	18	18
Employee benefit obligations	46	79
Compensation accruals	29	26
Credit carryforwards	12	11
Operating lease liabilities	98	69
Other	23	17
Valuation allowances	(32)	(30)
Net deferred tax assets	196	192
Deferred tax liabilities
Goodwill and other intangibles	16	11
Property, plant and equipment	109	75
Operating lease assets	78	67
Undistributed earnings	5	6
Total deferred tax liabilities	208	159
Total net deferred tax (liabilities) assets (e)	(12)
Total net deferred tax (liabilities) assets (e)		33
Operating Loss Carryforwards [Line Items]
Deferred income taxes	26	1
Deferred Tax Assets, Valuation Allowance	32	30
Deferred Tax Assets, Tax Deferred Expense	30
Unrecognized Tax Benefits	12	15	$ 14	$ 10
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	543	451	265
Income tax expense	$ 123	$ 134	$ 57
Common stock outstanding (in shares)	180	185
Tax Matters Agreement
Operating Loss Carryforwards [Line Items]
Unrecognized Tax Benefits	$ 33
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	27
Income tax expense	6
Majority Shareholder
Operating Loss Carryforwards [Line Items]
Ashland ownership percentage					83.00%
Expiration Years 2023 Through 2040 | Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	7
Expiration Years 2023 Through 2034 | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 361