Significant Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Standard [Member] | Palmarejo [Member]
Customers total revenue
Customers total revenue	$ 17.4	$ 14.5
Valcambi [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	12.2	107.9
Auramet [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	24.2	13.9
International Commodities [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	25.2	0
Mitsui [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	$ 22.4	$ 16.7
Sales Revenue, Segment [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	10.00%