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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses, Net of Tax		$ 2.1	$ 7.4	$ 4.9	$ 18.8
Amortization of prior service costs, Net of Tax		1.4	1.3	4.3	3.4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax			1.5		4.4
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses, Pre-tax	[1],[2]	(2.5)	(9.3)	(6.0)	(24.1)
Amortization of actuarial losses, Tax	[1],[2]	0.6	2.1	1.5	5.7
Amortization of actuarial losses, Net of Tax	[1],[2]	(1.9)	(7.2)	(4.5)	(18.4)
Amortization of prior service costs, Pre-Tax Amount	[1],[2]	(2.0)	(1.6)	(5.8)	(4.4)
Amortization of prior service costs, Tax	[1],[2]	0.5	0.3	1.5	1.0
Amortization of prior service costs, Net of Tax	[1],[2]	(1.5)	(1.3)	(4.3)	(3.4)
Defined Benefit Plans, before Tax	[1]	(4.5)	(10.9)	(11.8)	(28.5)
Defined Benefit Plans, Tax	[1]	1.1	2.4	3.0	6.7
Defined Benefit Plans, Net of Tax	[1]	(3.4)	(8.5)	(8.8)	(21.8)
Total Reclassifications From Other Comprehensive Income Before Tax	[1]	(4.5)	(13.0)	(11.8)	(34.5)
Total Reclassifications From Other Comprehensive Income Tax Portion	[1]	1.1	3.0	3.0	8.3
Total Reclassifications From Other Comprehensive Income Net of Tax	[1]	$ (3.4)	(10.0)	$ (8.8)	(26.2)
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	[1],[3]		(2.1)		(6.0)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[1],[3]		0.6		1.6
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[1],[3]		$ (1.5)		$ (4.4)

[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 4. Retirement Plans” for additional details.

[3] These accumulated other comprehensive loss components are included in Interest expense, net.