Mineral Properties, Development Costs and Exploration Rigths Narrative (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Purchase price for exploration right	$ 1,589,235	$ 1,589,235	$ 584,865
Payments to acquire exploration rights	8,200	8,167	0	0
Exploration rights
Property, Plant and Equipment [Line Items]
Purchase price for exploration right	$ 16,166	$ 16,166	$ 0
Sale of stock, price per share	$ 10.147	$ 10.147
Issuance of shares for investment in mining property	788,410