Equity and Other Comprehensive Income (Loss) - Summary of Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Mar. 31, 2024		Mar. 31, 2023		Mar. 31, 2024		Mar. 31, 2023
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization and settlement recognition of net actuarial loss, included in pension cost		$ 5.1		$ 10.1		$ 10.0		$ 19.8
Amortization of prior service costs, Net of Tax		1.6		1.4		2.7		2.8
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		9.1		20.1		13.0		30.0
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses, Pre-tax		(6.8)	[1],[2]	(13.2)	[1],[2]	(13.6)	[3],[4]	(26.5)	[3],[4]
Amortization of actuarial losses, Tax		1.7	[1],[2]	3.3	[1],[2]	3.6	[3],[4]	6.9	[3],[4]
Amortization and settlement recognition of net actuarial loss, included in pension cost		(5.1)	[1],[2]	(9.9)	[1],[2]	(10.0)	[3],[4]	(19.6)	[3],[4]
Amortization of prior service costs, Pre-Tax Amount		(2.2)	[1],[2]	(1.9)	[1],[2]	(3.7)	[3],[4]	(3.8)	[3],[4]
Amortization of prior service costs, Tax		0.6	[1],[2]	0.5	[1],[2]	1.0	[3],[4]	1.0	[3],[4]
Amortization of prior service costs, Net of Tax		(1.6)	[1],[2]	(1.4)	[1],[2]	(2.7)	[3],[4]	(2.8)	[3],[4]
Defined Benefit Plans, before Tax		(9.0)	[1]	(15.1)	[1]	(17.3)	[3]	(30.3)	[3]
Defined Benefit Plans, Tax		2.3	[1]	3.8	[1]	4.6	[3]	7.9	[3]
Defined Benefit Plans, Net of Tax		(6.7)	[1]	(11.3)	[1]	(12.7)	[3]	(22.4)	[3]
Recognition of previously unrealized foreign currency losses on consolidation of equity investment, Pre-tax	[3],[5]							(29.0)
Recognition of previously unrealized net foreign currency loss upon consolidation of equity investment	[3],[5]							(29.0)
Total Reclassifications From Other Comprehensive Income Before Tax		(21.0)	[1]	(41.9)	[1]	(34.5)	[3]	(99.3)	[3]
Total Reclassifications From Other Comprehensive Income Tax Portion		5.2	[1]	10.5	[1]	8.8	[3]	17.9	[3]
Total Reclassifications From Other Comprehensive Income Net of Tax		(15.8)	[1]	(31.4)	[1]	(25.7)	[3]	(81.4)	[3]
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		(12.0)	[1],[6]	(26.8)	[1],[6]	(17.2)	[3],[7]	(40.0)	[3],[7]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		2.9	[1],[6]	6.7	[1],[6]	4.2	[3],[7]	10.0	[3],[7]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		$ (9.1)	[1],[6]	$ (20.1)	[1],[6]	$ (13.0)	[3],[7]	$ (30.0)	[3],[7]

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

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

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

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

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