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, 2023		Mar. 31, 2022		Mar. 31, 2023		Mar. 31, 2022
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses, Net of Tax		$ 10.1		$ 1.5		$ 19.8		$ 2.8
Amortization of prior service costs, Net of Tax		1.4		1.5		2.8		2.9
Recognition of previously unrealized foreign currency losses on consolidation of equity investment, Net of Tax						29.0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		20.1				30.0
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses, Pre-tax		(13.2)	[1],[2]	(1.9)	[1],[2]	(26.5)	[3],[4]	(3.5)	[3],[4]
Amortization of actuarial losses, Tax		3.3	[1],[2]	0.5	[1],[2]	6.9	[3],[4]	0.9	[3],[4]
Amortization of actuarial losses, Net of Tax		(9.9)	[1],[2]	(1.4)	[1],[2]	(19.6)	[3],[4]	(2.6)	[3],[4]
Amortization of prior service costs, Pre-Tax Amount		(1.9)	[1],[2]	(1.9)	[1],[2]	(3.8)	[3],[4]	(3.8)	[3],[4]
Amortization of prior service costs, Tax		0.5	[1],[2]	0.5	[1],[2]	1.0	[3],[4]	1.0	[3],[4]
Amortization of prior service costs, Net of Tax		(1.4)	[1],[2]	(1.4)	[1],[2]	(2.8)	[3],[4]	(2.8)	[3],[4]
Defined Benefit Plans, before Tax		(15.1)	[1]	(3.8)	[1]	(30.3)	[3]	(7.3)	[3]
Defined Benefit Plans, Tax		3.8	[1]	1.0	[1]	7.9	[3]	1.9	[3]
Defined Benefit Plans, Net of Tax		(11.3)	[1]	(2.8)	[1]	(22.4)	[3]	(5.4)	[3]
Recognition of previously unrealized foreign currency losses on consolidation of equity investment, Pre-tax	[3],[5]					(29.0)
Recognition of previously unrealized foreign currency losses on consolidation of equity investment, Net of Tax	[3],[5]					(29.0)
Total Reclassifications From Other Comprehensive Income Before Tax		(41.9)	[1]	(3.8)	[1]	(99.3)	[3]	(7.3)	[3]
Total Reclassifications From Other Comprehensive Income Tax Portion		10.5	[1]	1.0	[1]	17.9	[3]	1.9	[3]
Total Reclassifications From Other Comprehensive Income Net of Tax		(31.4)	[1]	$ (2.8)	[1]	(81.4)	[3]	$ (5.4)	[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		(26.8)	[1],[6]			(40.0)	[3],[7]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		6.7	[1],[6]			10.0	[3],[7]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		$ (20.1)	[1],[6]			$ (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 6. 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 6. 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.