Significant Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Valcambi [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	$ 27.2	$ 148.3	$ 39.4	$ 256.2
Auramet [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	44.1	19.9	68.9	33.5
International Commodities [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	25.7	7.0	40.4	23.8
Mitsui [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	$ 34.5	$ 18.3	$ 44.8	$ 0.9
Sales Revenue, Segment [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	10.00%	10.00%	10.00%	10.00%