Sale of Metals and Related Costs (Details) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2015 USD ($) customer	Dec. 31, 2014 USD ($)
Sale of Metals and Related Costs
Number of customers to whom marketable products were sold \| customer	2
Inventory write down charged to cost of metals sold	$ 0.2	$ 1.2
Inventory write down charged to depreciation expense		$ 0.7

Charge to cost of goods sold that represents the reduction of the carrying amount of inventory, generally attributable to obsolescence or market conditions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 330

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28360613&loc=d3e4542-108314

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration