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Business Segments (Details3) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	$ 5,634.6	$ 5,501.8	$ 5,185.4
Deferred taxes	537.9	478.8
High Performance Materials & Components
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	2,689.9	2,765.4	2,662.3
Flat Rolled Products
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	2,255.8	2,225.7	2,218.4
Discontinued Operations [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	0.0	0.0	0.2
Corporate, Non-Segment [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Deferred taxes	64.5	8.7	7.6
Corporate: Cash and cash equivalents and other [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	$ 624.4	$ 502.0	$ 296.9

X

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
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-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 740
-SubTopic 10
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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