Accumulated Other Comprehensive (Loss)/Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (241.8)	$ (238.8)	$ (266.1)
OCI before reclassifications	(23.9)	(2.5)	20.0
Reclassifications to earnings	(14.1)	19.9	7.3
Reclassifications to retained earnings		(20.4)
Activity related to discontinued operations	(18.5)
Ending balance	(298.3)	(241.8)	(238.8)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(113.6)	(93.1)	(99.4)
OCI before reclassifications	9.0	(20.5)	6.3
Reclassifications to earnings	0.0	0.0	0.0
Reclassifications to retained earnings		0.0
Activity related to discontinued operations	(19.4)
Ending balance	(124.0)	(113.6)	(93.1)
Pension Activity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(136.4)	(139.4)	(159.9)
OCI before reclassifications	(29.5)	6.7	14.3
Reclassifications to earnings	(7.4)	16.2	6.2
Reclassifications to retained earnings		(19.9)
Activity related to discontinued operations
Ending balance	(173.3)	(136.4)	(139.4)
Foreign Currency Contracts \| Foreign Currency Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	3.3	(4.5)	(0.7)
OCI before reclassifications	6.3	4.8	(3.4)
Reclassifications to earnings	(6.5)	3.0	(0.4)
Reclassifications to retained earnings		0.0
Activity related to discontinued operations	0.0
Ending balance	3.1	3.3	(4.5)
Interest Rate Swap \| Foreign Currency Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	4.9	(1.8)	(6.1)
OCI before reclassifications	(9.0)	6.5	2.8
Reclassifications to earnings	(0.2)	0.7	1.5
Reclassifications to retained earnings		(0.5)
Activity related to discontinued operations	0.0
Ending balance	(4.3)	4.9	(1.8)
Zinc contracts \| Foreign Currency Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0.0	0.0	0.0
OCI before reclassifications	(0.7)	0.0	0.0
Reclassifications to earnings	0.0	0.0	0.0
Reclassifications to retained earnings		0.0
Activity related to discontinued operations	0.9
Ending balance	$ 0.2	$ 0.0	$ 0.0

Other Comprehensive Income (Loss), Effect of Discontinued Operations, Net of Tax

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- Definition

Reclassification from Accumulated Other Comprehensive Income, New Accounting Pronouncement or Change in Accounting Principle

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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