Equity and Other Comprehensive Income (Loss) - Summary of Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2023	Dec. 31, 2022
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization and settlement recognition of net actuarial loss, included in pension cost		$ 4.9	$ 9.7
Amortization of prior service costs, Net of Tax		1.1	1.4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		3.9	9.9
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses, Pre-tax	[1],[2]	(6.8)	(13.3)
Amortization of actuarial losses, Tax	[1],[2]	1.9	3.6
Amortization and settlement recognition of net actuarial loss, included in pension cost	[1],[2]	(4.9)	(9.7)
Amortization of prior service costs, Pre-Tax Amount	[1],[2]	(1.5)	(1.9)
Amortization of prior service costs, Tax	[1],[2]	0.4	0.5
Amortization of prior service costs, Net of Tax	[1],[2]	(1.1)	(1.4)
Defined Benefit Plans, before Tax	[1]	(8.3)	(15.2)
Defined Benefit Plans, Tax	[1]	2.3	4.1
Defined Benefit Plans, Net of Tax	[1]	(6.0)	(11.1)
Recognition of previously unrealized foreign currency losses on consolidation of equity investment, Pre-tax	[1],[3]		(29.0)
Recognition of previously unrealized net foreign currency loss upon consolidation of equity investment	[1],[3]		(29.0)
Total Reclassifications From Other Comprehensive Income Before Tax	[1]	(13.5)	(57.4)
Total Reclassifications From Other Comprehensive Income Tax Portion	[1]	3.6	7.4
Total Reclassifications From Other Comprehensive Income Net of Tax	[1]	(9.9)	(50.0)
Parent [Member] | Natural Gas Commodity Hedge [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[1],[4]	(5.2)	(13.2)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[1],[4]	1.3	3.3
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[1],[4]	$ (3.9)	$ (9.9)

[1] Amounts in parentheses indicate charges to earnings. Amounts pertaining to noncontrolling interests are excluded.

[2] Included in the computation of net periodic pension cost. See “Note 5. Retirement Plans” for additional details.

[3] Amount reflected in Equity in income (loss) of unconsolidated entities in the consolidated statements of operations.

[4] These accumulated other comprehensive loss components are included in Cost of goods sold.