Significant Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Valcambi [Member] | Palmarejo San Bartolome [Member]
Customers total revenue
Customers total revenue	$ 107.9	$ 52.6
Auramet [Member] | Palmarejo [Member]
Customers total revenue
Customers total revenue	13.9	29.9
China Gold [Member] | Kensington [Member]
Customers total revenue
Customers total revenue	4.6	48.1
International Commodities [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	16.8	46.2
Mitsui [Member] | Palmarejo San Bartolome Rochester [Member]
Customers total revenue
Customers total revenue	$ 0	$ 0
Sales Revenue, Segment [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	10.00%