Description of the Business and Significant Accounting Policies (Details)	3 Months Ended
	Mar. 31, 2015 facility	Mar. 31, 2014
Description of the Business and Significant Accounting Policies
Number of reporting segments	3
Steel Operations
Segment Reporting Information
Percentage of external net sales	68.00%	61.00%
Number of downstream finishing facilities	8
Metals Recycling/Ferrous Resources
Segment Reporting Information
Percentage of external net sales	23.00%	32.00%
Number of ironmaking initiatives	2
Steel Fabrication Operations
Segment Reporting Information
Percentage of external net sales	8.00%	6.00%
Number of New Millennium Building Systems' joist and deck plants	6