Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			8 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Aug. 31, 2010 Cerro Bayo Mine [Member]	Dec. 31, 2010 Cerro Bayo Mine [Member]
Financial information included in income from discontinued operations
Depreciation and depletion					$ (2,194)
Administrative and general					(18)
Care and maintenance and other					(2,351)
Other income and expense					(145)
Income tax expense					(1,321)
Income from discontinued operations					(6,029)
Gain (loss) on sale of net assets of discontinued operations, net of taxes of $0.0 million for 2010 and $6.5 million for 2009	0	0	(2,095)	0	(2,095)
Total					$ (8,124)