Acquisitions and Divestitures - 2014 Divestiture - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2014 USD ($) Mills	Dec. 31, 2013 USD ($) Employees
2014 Divestitures [Member]
Business Acquisition [Line Items]
Net cash proceeds	$ 24
Loss from divestitures before income tax	$ (116)
Atlas Holdings LLC [Member]
Business Acquisition [Line Items]
Number of rolling mills \| Mills	3
Number of employees \| Employees		750
Sale generated in last annual period prior to divestiture		$ 500

Number of employees.

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- Definition

Number Of Mills Located.

+ References

No definition available.

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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.

+ Details

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- Definition

Amount before tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
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- Definition

Amount of revenue attributable to disposal group, including, but not limited to, discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

This element represents the cash inflow during the period from the sale of a component of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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