Other-net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of other-net expense
Metal consignment fees	$ 10,999	$ 8,782	$ 6,409
Amortization of Intangible Assets	2,265	4,629	4,498
Foreign currency loss (gain)	1,487	(722)	1,525
Net loss (gain) on disposal of fixed assets	518	234	(648)
Rental Income	(416)	(168)	(21)
Other items	481	1,138	(475)
Total	$ 15,334	$ 13,893	$ 11,288