Equity and Other Comprehensive Income (Loss) - Summary of Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization and settlement recognition of net actuarial loss, included in pension cost		$ 8.7	$ 4.9
Amortization of prior service costs, Net of Tax		0.5	0.5
Reclassification of stranded tax effects	[1]	73.4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		(1.3)
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net actuarial loss, Pre-Tax Amount	[2],[3]	(11.6)	(6.6)
Amortization of net actuarial loss, Tax	[2],[3]	3.0	1.7
Amortization and settlement recognition of net actuarial loss, included in pension cost	[2],[3]	(8.6)	(4.9)
Amortization of prior service costs, Pre-Tax Amount	[2],[3]	(0.7)	(0.6)
Amortization of prior service costs, Tax	[2],[3]	0.2	0.1
Amortization of prior service costs, Net of Tax	[2],[3]	(0.5)	(0.5)
Defined Benefit Plans, before Tax	[2]	(12.3)	(7.2)
Defined Benefit Plans, Tax	[2]	76.6	1.8
Defined Benefit Plans, Net of Tax	[2]	64.3	(5.4)
Total Reclassifications From Other Comprehensive Income Before Tax	[2]	(10.5)	(7.2)
Total Reclassifications From Other Comprehensive Income Tax Portion	[2]	76.1	1.8
Total Reclassifications From Other Comprehensive Income Net of Tax	[2]	65.6	$ (5.4)
Parent [Member] | Cash Flow Hedges [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[2]	1.8
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2]	(0.5)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2]	1.3
Parent [Member] | ASU 2018-02 [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification of stranded tax effects	[4]	73.4
Parent [Member] | Interest Rate Contract [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[2],[5]	0.7
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2],[5]	(0.2)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2],[5]	0.5
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	[2],[6]	1.1
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2],[6]	(0.3)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2],[6]	$ 0.8

[1] All amounts are net of tax and noncontrolling interests.

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

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

[4] Amount reclassified to retained earnings as a result of the adoption of ASU 2018-02.

[5] These accumulated other comprehensive income components are included in interest expense, net.

[6] These accumulated other comprehensive income components are included in cost of goods sold.