Significant Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Standard [Member] | Palmarejo [Member]
Customers total revenue
Customers total revenue	$ 17.5	$ 36.0	$ 42.0	$ 86.4
Valcambi [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	112.7	112.4
Valcambi [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue			368.9	255.3
Auramet [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	32.0	0
China Gold [Member] | Kensington [Member]
Customers total revenue
Customers total revenue			25.7	94.4
International Commodities [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	10.8	47.0	34.7	93.3
Mitsui [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	$ 14.2	$ 49.9	$ 40.1	$ 81.9
Sales Revenue, Segment [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	10.00%		10.00%