Derivative Financial Instruments (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Revenue	$ 166,263	$ 164,562	$ 319,219		$ 324,195
Costs applicable to sales	119,097	118,687	234,160	[1]	225,583	[1]
Fair value adjustments, net	2,754	(8,282)	(2,130)		(19,717)
Fair value adjustments, net	994	(6,438)	(684)		(17,259)
Concentrate Sales Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(623)	7	291		872
Forward foreign exchange contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Costs applicable to sales	0	10	0		(924)
Fair value adjustments, net	0	(10)	0		957
Mexican peso forward purchase contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value adjustments, net	0	0	0		957
Silver and gold options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives			1,000		$ (2,868)
Fair value adjustments, net	$ 1,232	$ (1,374)	$ 185

[1] Excludes amortization.