Description of the Business and Significant Accounting Policies (Segments) (Details) - segment	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 01, 2019
Segment Reporting Information
Number of reporting segments			3
Steel Operations
Segment Reporting Information
Percentage of external net sales	76.00%	77.00%	76.00%	75.00%
Metals Recycling Operations
Segment Reporting Information
Percentage of external net sales	11.00%	12.00%	12.00%	14.00%
Steel Fabrication Operations
Segment Reporting Information
Percentage of external net sales	10.00%	8.00%	9.00%	8.00%
United Steel Supply, LLC
Segment Reporting Information
Acquisition of interest (as a percent)					75.00%