Basis of Presentation and Major Accounting Policies (Narrative) (Details)	3 Months Ended		12 Months Ended
	Jun. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) plant segment	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Accounting Policies [Abstract]
Number of reportable segments | segment			5
Excluded components recognized within earnings			$ 20,400,000	$ 31,400,000	$ 25,100,000
Environmental expenditures			$ 37,700,000	$ 27,000,000.0	$ 24,900,000
Environmental Remediation Expense, Statement of Income or Comprehensive Income [Extensible Enumeration]			Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Pre-tax loss from discontinued operations	$ 10,600,000	$ 19,400,000	$ 10,600,000	$ 19,400,000
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, residual value			0
Restructuring Cost and Reserve [Line Items]
Plant and equipment, net		23,370,900,000	$ 25,337,800,000	23,370,900,000	$ 17,472,100,000
Project Exit Costs
Restructuring Cost and Reserve [Line Items]
Number of plants to be disposed of | plant			2
Project Exit Costs | Fair Value, Nonrecurring
Restructuring Cost and Reserve [Line Items]
Plant and equipment, net			$ 22,500,000
Assets held for sale			$ 418,300,000
Computer software costs | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life			3 years
Computer software costs | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life			5 years
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life			5 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life			25 years
Patents and technology | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life			5 years
Patents and technology | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life			15 years
Land Use Rights
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life			50 years
Discontinued Operations
Disclosures by Disposal Group [Line Items]
Assets of discontinued operations		0	$ 0	0
Liabilities of discontinued operations		$ 0	$ 0	$ 0