Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Jan. 29, 2013
Assets:
Total assets	$ 63,621	$ 14,656
Liabilities:
Total liabilities	50,361	63,559
Royalty obligation embedded derivative [Member]
Liabilities:
Derivative fair value of derivative liability		40,338
Rochester Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability		21,630
Other Derivative Instrument [Member]
Liabilities:
Derivative fair value of derivative liability	501	1,591
Gold Put Purchase and Call Sold Options Net [Member]
Assets:
Fair value of derivative asset	4,939
Liabilities:
Derivative fair value of derivative liability	1,331
Short-term Deposit [Member]
Assets:
Short-term Deposits	49,520	14,521
Marketable securities [Member]
Assets:
Restricted certificates of deposits	9,162	135
Fair Value, Inputs, Level 1 [Member]
Assets:
Total assets	58,682	14,521
Liabilities:
Total liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Royalty obligation embedded derivative [Member]
Liabilities:
Derivative fair value of derivative liability	0	0
Fair Value, Inputs, Level 1 [Member] | Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability	0
Fair Value, Inputs, Level 1 [Member] | Rochester Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability		0
Fair Value, Inputs, Level 1 [Member] | Other Derivative Instrument [Member]
Liabilities:
Derivative fair value of derivative liability	0	0
Fair Value, Inputs, Level 1 [Member] | Gold Put Purchase and Call Sold Options Net [Member]
Assets:
Fair value of derivative asset	0
Liabilities:
Derivative fair value of derivative liability	0
Fair Value, Inputs, Level 1 [Member] | Short-term Deposit [Member]
Assets:
Short-term Deposits	49,520	14,521
Fair Value, Inputs, Level 1 [Member] | Marketable securities [Member]
Assets:
Restricted certificates of deposits	9,162	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Total assets	4,939	135
Liabilities:
Total liabilities	1,832	1,591
Fair Value, Inputs, Level 2 [Member] | Royalty obligation embedded derivative [Member]
Liabilities:
Derivative fair value of derivative liability	0	0
Fair Value, Inputs, Level 2 [Member] | Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability	0
Fair Value, Inputs, Level 2 [Member] | Rochester Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability		0
Fair Value, Inputs, Level 2 [Member] | Other Derivative Instrument [Member]
Liabilities:
Derivative fair value of derivative liability	501	1,591
Fair Value, Inputs, Level 2 [Member] | Gold Put Purchase and Call Sold Options Net [Member]
Liabilities:
Derivative fair value of derivative liability	1,331
Fair Value, Inputs, Level 2 [Member] | Short-term Deposit [Member]
Assets:
Short-term Deposits	0	0
Fair Value, Inputs, Level 2 [Member] | Marketable securities [Member]
Assets:
Restricted certificates of deposits	0	135
Fair Value, Inputs, Level 3 [Member]
Assets:
Total assets	0	0
Liabilities:
Total liabilities	48,529	61,968
Fair Value, Inputs, Level 3 [Member] | Royalty obligation embedded derivative [Member]
Liabilities:
Derivative fair value of derivative liability	30,261	40,338
Fair Value, Inputs, Level 3 [Member] | Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability	18,268
Fair Value, Inputs, Level 3 [Member] | Rochester Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability		21,630
Fair Value, Inputs, Level 3 [Member] | Other Derivative Instrument [Member]
Liabilities:
Derivative fair value of derivative liability	0	0
Fair Value, Inputs, Level 3 [Member] | Gold Put Purchase and Call Sold Options Net [Member]
Assets:
Fair value of derivative asset	0
Liabilities:
Derivative fair value of derivative liability	0
Fair Value, Inputs, Level 3 [Member] | Short-term Deposit [Member]
Assets:
Short-term Deposits	0	0
Fair Value, Inputs, Level 3 [Member] | Marketable securities [Member]
Assets:
Restricted certificates of deposits	0	0
Prepaid Expenses and Other Current Assets [Member]
Assets:
Fair value of derivative asset	4,962	184
Prepaid Expenses and Other Current Assets [Member] | Palmarejo gold production royalty [Member]
Assets:
Fair value of derivative asset
Prepaid Expenses and Other Current Assets [Member] | Gold Put Purchase and Call Sold Options Net [Member]
Assets:
Fair value of derivative asset	4,939	135
Palmarejo Royalty Obligation [Member] | Royalty obligation embedded derivative [Member]
Liabilities:
Derivative fair value of derivative liability	30,261
Rochester Royalty Obligation [Member] | Royalty Obligation [Member]
Liabilities:
Derivative fair value of derivative liability	$ 18,268
Convertible Senior Notes Due March 2028 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.25%	3.25%
Senior Notes due Two Thousand Twenty One [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.875%	7.875%	7.875%