Fair Value Measurements Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Convertible Senior Notes Due March 2028 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Convertible Senior Notes Due March 2028 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	$ 46,833	$ 49,205
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Convertible Senior Notes Due March 2028 [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	46,833	49,205
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Convertible Senior Notes Due March 2028 [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	0	0
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Convertible Senior Notes Due March 2028 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	0	0
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Palmarejo gold production royalty [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	100,054	111,257
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Palmarejo gold production royalty [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	0	0
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Palmarejo gold production royalty [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	100,054	111,257
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Palmarejo gold production royalty [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	$ 0	$ 0