Segment Reporting Segment Reporting - Segment Information for Total Assets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
Assets	$ 774,792		$ 788,806
Metals segment
Segment Reporting Information [Line Items]
Assets	678,352		693,803
Plastics segment
Segment Reporting Information [Line Items]
Assets	58,808		56,149
Other
Segment Reporting Information [Line Items]
Assets	$ 37,632	[1]	$ 38,854	[1]

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