Other Comprehensive Income (Loss) - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Affected Line in the Consolidated Statement of Operations:
Revenues	$ 2,673.8	$ 3,182.8	$ 2,826.0
Cost of goods sold	(1,773.0)	(2,126.3)	(1,877.8)
Gain on divestiture of discontinued operations (net of income tax expense)	0.0	0.0	443.1
Tax expense	54.5	(64.8)	(102.8)
Total reclassifications for the period, net of tax	(5.9)	5.1	(0.3)
Pension and Postretirement
Affected Line in the Consolidated Statement of Operations:
Total reclassifications for the period, net of tax	(4.0)	25.3	(1.3)
Net Unrealized (Loss) Gain on Derivative Instruments
Affected Line in the Consolidated Statement of Operations:
Total reclassifications for the period, net of tax	3.7	(20.2)	1.0
Currency Translation (1)
Affected Line in the Consolidated Statement of Operations:
Total reclassifications for the period, net of tax	(5.6)	0.0	0.0
Reclassification out of Accumulated Other Comprehensive Income
Affected Line in the Consolidated Statement of Operations:
Revenues	0.1	0.5	(0.1)
Cost of goods sold	(0.1)	0.3	(1.3)
Other Nonoperating Income (Expense)	(2.7)	(14.1)	(2.1)
Gain on divestiture of discontinued operations (net of income tax expense)	(11.0)		(1.5)
Income before income taxes	(8.3)	14.9	(0.8)
Tax expense	2.4	(9.8)	0.5
Total reclassifications for the period, net of tax	(5.9)	5.1	(0.3)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment Net Loss Recognized
Affected Line in the Consolidated Statement of Operations:
Revenues	0.0	0.0	0.0
Cost of goods sold	0.0	0.0	0.0
Other Nonoperating Income (Expense)	1.2	(35.0)	(0.1)
Gain on divestiture of discontinued operations (net of income tax expense)	(5.2)		(1.4)
Income before income taxes	(6.4)	35.0	(1.3)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment Prior Service Cost Recognized
Affected Line in the Consolidated Statement of Operations:
Revenues	0.0	0.0	0.0
Cost of goods sold	0.0	0.0	0.0
Other Nonoperating Income (Expense)	0.0	0.0	0.0
Gain on divestiture of discontinued operations (net of income tax expense)	0.0		(0.1)
Income before income taxes	0.0	0.0	(0.1)
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized (Loss) Gain on Derivative Instruments
Affected Line in the Consolidated Statement of Operations:
Revenues	0.1	0.5	(0.1)
Cost of goods sold	(0.1)	0.3	(1.3)
Other Nonoperating Income (Expense)	(3.9)	20.9	(2.0)
Gain on divestiture of discontinued operations (net of income tax expense)	(0.2)		0.0
Income before income taxes	3.7	$ (20.1)	$ 0.6
Reclassification out of Accumulated Other Comprehensive Income | Currency Translation (1)
Affected Line in the Consolidated Statement of Operations:
Revenues	0.0
Cost of goods sold	0.0
Other Nonoperating Income (Expense)	0.0
Gain on divestiture of discontinued operations (net of income tax expense)	(5.6)
Income before income taxes	$ (5.6)