Fair Value Measurements (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Palmarejo Royalty Obligation [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	$ 21,912	$ 40,338
Revaluation	(3,101)	2,001
Settlements	(13,854)	(20,427)
Balance at the end of the period	4,957	21,912
Rochester Royalty Obligation [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	15,370	21,630
Revaluation	(818)	(3,653)
Settlements	(4,959)	(2,607)
Balance at the end of the period	9,593	15,370
Available-for-sale Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	1,379
Revaluation	(983)
Settlements	(386)
Balance at the end of the period	$ 10	$ 1,379