Description of the Business and Significant Accounting Policies (Goodwill) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Goodwill
Goodwill	$ 390,129	$ 393,351
OmniSource
Goodwill
Goodwill decrease due to tax benefit related to the normal amortization of the component	3,200
Steel Operations | Columbus Flat Roll Division
Goodwill
Goodwill	19,682	19,682
Steel Operations | The Techs
Goodwill
Goodwill	142,783	142,783
Steel Operations | Vulcan Steel Products [Member]
Goodwill
Goodwill	7,824	7,824
Steel Operations | Roanoke Bar Division
Goodwill
Goodwill	29,041	29,041
Metals Recycling Operations | Butler Flat Roll Division, Structural and Rail Division, and Engineered Bar Division
Goodwill
Goodwill	95,000	95,000
Metals Recycling Operations | OmniSource
Goodwill
Goodwill	93,874	97,096
Steel Fabrication Operations | New Millennium Building Systems
Goodwill
Goodwill	$ 1,925	$ 1,925