Basis of Presentation (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended	12 Months Ended
Jul. 02, 2012	Jun. 30, 2012	Dec. 31, 2013	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of mining complexes operated		4
number of mining complexes temporarily idled			1
Purchase of noncontrolling interest	$ 17,500		$ 0	$ 0

The cash outflow associated with the purchase of noncontrolling interest during the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration