Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2024	Sep. 28, 2016
Income Tax Contingency [Line Items]
Income Tax Benefit	$ 29.0
Deferred Income Taxes and Tax Credits	25.7
Other noncurrent liabilities	346.8	$ 373.3
Deferred tax assets, valuation allowance	3.0	1.0
Tax Year 2023
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance	27.1
Majority Shareholder
Income Tax Contingency [Line Items]
Ashland ownership percentage			83.00%
Tax Matters Agreement | Ashland | Affiliated Entity
Income Tax Contingency [Line Items]
Other noncurrent liabilities	$ 10.8	$ 9.0