Fair Value Measurements (Details 2) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Equity Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	$ 7	$ 10
Revaluation	0	0
Settlements	0	(3)
Balance at the end of the period	7	7
Palmarejo Royalty Obligation [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	3,317	4,957
Revaluation	110	5,866
Settlements	(3,427)	(10,823)
Balance at the end of the period	0	0
Rochester Royalty Obligation [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	12,559	9,593
Revaluation	851	5,787
Settlements	(1,132)	(3,102)
Balance at the end of the period	$ 12,278	$ 12,278