Fair Value Measurements (Details 2) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 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	6,827	4,957
Revaluation	878	5,756
Settlements	(4,388)	(7,396)
Balance at the end of the period	3,317	3,317
Rochester Royalty Obligation [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	10,877	9,593
Revaluation	2,687	4,936
Settlements	(1,005)	(1,970)
Balance at the end of the period	$ 12,559	$ 12,559