Segment Reporting Segment Reporting - Segment Information for Total Assets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Segment Reporting Information [Line Items]
Assets	$ 592,276		$ 587,976
Metals segment
Segment Reporting Information [Line Items]
Assets	491,447		489,563
Plastics segment
Segment Reporting Information [Line Items]
Assets	62,826		60,970
Other
Segment Reporting Information [Line Items]
Assets	$ 38,003	[1]	$ 37,443	[1]

[1] “Other” — Total assets consist of the Company's investment in joint venture.