Significant Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Auramet [Member] | Kensington [Member]
Customers total revenue
Customers total revenue	$ 28.5	$ 32.0
Auramet [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue			97.4	65.5
Valcambi [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	22.5	112.7	61.9	368.9
International Commodities [Member] | Palmarejo [Member]
Customers total revenue
Customers total revenue	41.5	10.8
International Commodities [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue			82.0	34.7
Mitsui [Member] | Palmarejo [Member]
Customers total revenue
Customers total revenue	0	0
TD Bank Group [Member] | Palmarejo [Member]
Customers total revenue
Customers total revenue	28.9	19.4	78.1	44.6
China Gold [Member] | Kensington [Member]
Customers total revenue
Customers total revenue	$ 21.3	$ 9.6
Sales Revenue, Segment [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	10.00%	10.00%	10.00%	10.00%