Business Segments (Details) $ in Millions	3 Months Ended
Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Number of business segments \| segment	2
Segment Reporting Information [Line Items]
Sales	$ 865.9	$ 757.5
Operating profit (loss):	69.9	(80.5)
LIFO and net realizable value reserves	0.0	0.0
Corporate expenses	(10.3)	(11.0)
Closed operations and other expenses	(3.0)	(3.5)
Restructuring and other charges	0.0	(9.0)
Interest expense, net	(33.5)	(28.3)
Income (loss) before income tax provision (benefit)	23.1	(132.3)
High Performance Materials & Components
Segment Reporting Information [Line Items]
Operating profit (loss):	50.9	29.1
Flat Rolled Products
Segment Reporting Information [Line Items]
Operating profit (loss):	19.0	(109.6)
Operating Segments
Segment Reporting Information [Line Items]
Sales	896.7	789.1
Operating Segments \| High Performance Materials & Components
Segment Reporting Information [Line Items]
Sales	523.7	507.9
Operating Segments \| Flat Rolled Products
Segment Reporting Information [Line Items]
Sales	373.0	281.2
Internal Customers \| Operating Segments
Segment Reporting Information [Line Items]
Sales	30.8	31.6
Internal Customers \| Operating Segments \| High Performance Materials & Components
Segment Reporting Information [Line Items]
Sales	13.3	14.9
Internal Customers \| Operating Segments \| Flat Rolled Products
Segment Reporting Information [Line Items]
Sales	17.5	16.7
External Customers \| Operating Segments
Segment Reporting Information [Line Items]
Sales	865.9	757.5
External Customers \| Operating Segments \| High Performance Materials & Components
Segment Reporting Information [Line Items]
Sales	510.4	493.0
External Customers \| Operating Segments \| Flat Rolled Products
Segment Reporting Information [Line Items]
Sales	$ 355.5	$ 264.5

corporate office expenses not allocable to business segments

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Restructuring and other charges

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Business segment operating profit, which excludes costs for restructuring charges, retirement benefit income or expense, corproate expenses, interest expense, debt extinguishment costs and costs associated with closed operations. These costs are excluded for segment reporting to provide a profit measure based on what management considers to be controllable costs at the business segment level

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(a))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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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.

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