Segment Reporting (Details 3) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) trading_counterparty	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 662,497	$ 639,236	$ 632,526
Dore [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of Trading Counterparties | trading_counterparty	11
Smelting and Refining [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of Trading Counterparties | trading_counterparty	2
Sales [Member] | Dore [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration Risk, Percentage	77.00%	74.00%	63.00%
Sales [Member] | Smelting and Refining [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration Risk, Percentage	23.00%	26.00%	37.00%
Mitsui & Co. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 0	$ 137,700	$ 133,800
China National Gold [Domain]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	126,600	126,200	86,800
Ohio Precious Metals [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	98,400	37,300	8,300
Republic Metals Corporation [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	93,300	47,700	4,000
Asahi Formerly Johnson Matthey [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	62,600	84,200	71,800
Standard Bank [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	29,000	34,700	87,500
TD Securities [Domain]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	15,500	81,300	106,700
INTL Commodities [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 76,700	$ 33,100	$ 22,400