Inventory (Major Classes of Inventory) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials and starting stock	$ 9,555	$ 8,527
Semi-finished and finished steel products	115,627	99,820
Operating materials	12,515	10,850
Gross inventory	137,697	119,197
Inventory reserves	(2,959)	(2,534)
Total inventory, net	$ 134,738	$ 116,663