Fair Value Measurements (Details 4) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 468,570	$ 306,130
Senior Notes due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	452,855	300,000
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]
Convertible Debt, Fair Value Disclosures	5,047	5,067
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]
Convertible Debt, Fair Value Disclosures	0	5,067
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]
Convertible Debt, Fair Value Disclosures	5,047	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]
Convertible Debt, Fair Value Disclosures	0	0
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Senior Notes due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	455,625	307,314
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Senior Notes due 2021 [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	0	307,314
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Senior Notes due 2021 [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	455,625	0
Portion at Other than Fair Value, Fair Value Disclosure [Member] | Senior Notes due 2021 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	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	51,252	65,212
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	0	0
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	51,252	65,212
Reported Value Measurement [Member] | Convertible Senior Notes Due March 2028 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible Debt, Fair Value Disclosures	5,334	5,334
Reported Value Measurement [Member] | Senior Notes due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		300,000
Reported Value Measurement [Member] | Palmarejo gold production royalty [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Liabilities Not Measured at Fair Value	$ 41,976	$ 51,193