Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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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.

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Description of the Business and Summary of Significant Accounting Policies (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill
Goodwill	$ 745,158,000us-gaap_Goodwill	$ 731,996,000us-gaap_Goodwill
Equity-Based Compensation
Compensation expense for stock options	22,800,000	15,200,000	9,900,000
Omni Source - Metals Recycling/Ferrous Resources Segment
Goodwill
Goodwill	456,727,000	463,247,000
Goodwill decrease due to tax benefit related to the amortization of the component	6,500,000
The Techs - Steel Segment
Goodwill
Goodwill	142,783,000	142,783,000
Butler Flat Roll Division, Structural and Rail Division, and Engineered Bar Division - Metals Recycling/Ferrous Resources Segment
Goodwill
Goodwill	95,000,000	95,000,000
Roanoke Bar Division - Steel Segment
Goodwill
Goodwill	29,041,000	29,041,000
Columbus Flat Roll Division
Goodwill
Goodwill	19,682,000
New Millennium Building Systems - Steel Fabrication Segment
Goodwill
Goodwill	$ 1,925,000	$ 1,925,000