Fair Value Measurements (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Equity Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	$ 10	$ 1,379
Revaluation	272	(983)
Settlements	(3)	(386)
Balance at the end of the period	279	10
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	21,912
Revaluation	5,866	(3,101)
Settlements	(10,823)	(13,854)
Balance at the end of the period	0	4,957
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	15,370
Revaluation	4,133	(818)
Settlements	(4,439)	(4,959)
Balance at the end of the period	$ 9,287	$ 9,593