Business combinations - Schedule of Activity Associated with Goodwill (Detail) $ in Millions	9 Months Ended
Sep. 30, 2015 USD ($)
Business Combinations [Abstract]
Preliminary purchase price allocation for the Real Alloy Acquisition reported as of March 31, 2015	$ 102.3
Adjustments to preliminary purchase price allocation for the Real Alloy Acquisition recorded in the quarter ended June 30, 2015	(17.8)
Adjustments to preliminary purchase price allocation for the Real Alloy Acquisition recorded in the quarter ended September 30, 2015	0.5
Balance at end of period	$ 85.0

No definition available.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 20

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

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-Publisher FASB

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- Definition

The amount of an adjustment to a previously reported goodwill impairment charge, which will be recognized in the subsequent reporting period.

+ References

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- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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