Equity and Other Comprehensive Income (Loss) - Summary of Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization and settlement recognition of net actuarial loss, included in pension cost		$ 9.0	$ 4.5	$ 26.2	$ 12.6
Amortization of prior service costs, Net of Tax		1.0	0.4	2.5	1.3
Reclassification of stranded tax effects	[1]			73.4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		1.0		2.2
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net actuarial loss, Pre-Tax Amount	[2],[3]	(11.4)	(5.9)	(34.5)	(16.6)
Amortization of net actuarial loss, Tax	[2],[3]	2.6	1.5	8.7	4.3
Amortization and settlement recognition of net actuarial loss, included in pension cost	[2],[3]	(8.8)	(4.4)	(25.8)	(12.3)
Amortization of prior service costs, Pre-Tax Amount	[2],[3]	(1.3)	(0.5)	(3.3)	(1.7)
Amortization of prior service costs, Tax	[2],[3]	0.3	0.1	0.8	0.4
Amortization of prior service costs, Net of Tax	[2],[3]	(1.0)	(0.4)	(2.5)	(1.3)
Defined Benefit Plans, before Tax	[2]	(12.7)	(6.4)	(37.8)	(18.3)
Defined Benefit Plans, Tax	[2]	2.9	1.6	82.9	4.7
Defined Benefit Plans, Net of Tax	[2]	(9.8)	(4.8)	45.1	(13.6)
Total Reclassifications From Other Comprehensive Income Before Tax	[2]	(14.1)	(6.4)	(40.8)	(18.3)
Total Reclassifications From Other Comprehensive Income Tax Portion	[2]	3.2	1.6	83.7	4.7
Total Reclassifications From Other Comprehensive Income Net of Tax	[2]	(10.9)	$ (4.8)	42.9	$ (13.6)
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]			(3.0)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2]			0.8
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2]			(2.2)
Parent [Member] | ASU 2018-02 [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification of stranded tax effects	[4]			73.4
Reclassification of stranded tax effects net	[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]	(1.4)		(0.4)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2],[5]	0.3		0.1
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2],[5]	$ (1.1)		(0.3)
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	[2],[6]			(2.6)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2],[6]			0.7
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2],[6]			$ (1.9)

[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.