Fair Value Measurements (Details 2) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Equity Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	$ 10
Revaluation	0
Settlements	(3)
Balance at the end of the period	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	4,957
Revaluation	4,878
Settlements	(3,008)
Balance at the end of the period	6,827
Rochester Royalty Obligation [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	9,593
Revaluation	2,249
Settlements	(965)
Balance at the end of the period	$ 10,877